This company is local to me and I have heard a lot of good things from them in the startup communities here. http://tealium.com/

You'll definitely want to checkout Segment.com. Not only do they provide a ton of integrations to send data to various apps, they also give you the ability to send that data into a data warehouse that you control, like Postgresql or Redshift.

This gives you the ability to join and visualize that data later with tools like Mode Analytics, Looker, or Chart.io.

We will investigate Tag Management briefly before moving on to the solution, because it is highly essential to know what Tag Management and how it works before we know that solutions we have.
A tag management solution or system (TMS) allows you to keep all the tags on your website inside of a single master set of code. That means your employees no longer need to work directly with the code for each tag that needs to be added, deleted, or modified. They also will not need to send a request to IT for any tag management, because the TMS provides an interface that allows employees to control how the TMS deploys tags. Besides being convenient, a TMS can make your web pages load more quickly by controlling the way your tags load. It can save you money by reducing the number of duplicate tags you may be paying for unnecessarily. It can also help you follow data privacy laws better. A TMS provides an easy-to-use interface. With it, non-IT professionals can set rules about when each tag will “fire” (run). Marketers, analysts, and others who are authorized can access and update these rules. One of the most common and serious problems on company websites is broken tags. On a large corporate website, it is easy for tags to be lost, wrongly duplicated, unauthorized, and poorly configured, because they are running so many times across so many web pages. A TMS allows you to see and correct many of these problems in one place. The interface may even allow employees to select, delete, and edit tags with the click of a mouse.
Once you have understood what tag management solution is and how it works, we will now look at the solutions. You have already said that you have tried Google GTM, so I will not discuss it anymore.
1. Launch by Adobe: Launch by Adobe is Adobe’s new tag management platform to replace Dynamic Tag Management (or Activation). Using Launch’s open APIs, tag managers can quickly and easily integrate their top marketing technologies. Launch works with both Adobe and non-Adobe products.
Features:
a) Simple interface for both technical and non-technical users
b) Free to Adobe Marketing Cloud customers
c) Marketing-friendly rule builder to determine when to deploy tags and what data to capture
d) Extension catalogue to make deploying new tags a quick, user-friendly process

2. Tealium: Tealium is a heavyweight in the TMS world, powering 25 percent of the top 100 Internet Retailers with their TMS solution, and is a great solution to consider for organizations with complex requirements or more than one high-traffic website.
Tealium allows for easy deployment and management of web tags, while giving digital marketers the ability to try out new technologies and take control of their marketing technology stack.
Features:
a) High amount of turnkey integrations
b) Controlled, secure deployments
c) Robust privacy capabilities
d) Powerful variables and load rules management

3. Signal: With Signal Tag Management, practitioners can focus less on wrangling code and more on innovation. Like any TMS system, Signal Tag Management helps marketers improve digital user experience by speeding up website load times. Signal is extremely focused on advertising tags.
Features:
a) Free for Signal Fuse customers
b) Preview, activate and deactivate on your own schedule
c) Built-in privacy policies allowing users to opt-out
d) Expert support for help when you need it

4. Qubit: Qubit runs a tag management system called Open tag, which is built for marketers, but customizable for developers. Open tag is a sleek, easy-to-use solution to tag management.
Features:
a. Clean, modern design that supports easy navigation
b. Flexible user management
c. Integrated with A/B testing
d. Asynchronous tag loading

5. Ensighten: Ensighten Manage is well suited in security-focused, policy and process-driven, highly collaborative environments where marketers need technical flexibility to meet the demands of configuring and deploying a variety of web tagging requirements.
Features:
a. User roles and security access can be thoroughly defined
b. Offers reliable and redundant data centres
c. Can track Mobile App user engagement
d. Collects omnichannel first party data
As one of the market leaders, Ensighten offers great insight around tag management research and best practices on their company blog.
6. TagCommander: Based in Europe, TagCommander integrates with hundreds of tag solutions worldwide. TagCommander enables users to boost marketing agility and performance across both web and mobile platforms. Real-time conversion deduplication and easy compliance to data privacy legislation are just two of the many benefits of TagCommander.
Features:
a) Provides enterprise-level support and service
b) Offers role-based permissions, intuitive workflows and full audit trails
c) Over 800 turnkey templates available
d) No technical knowledge required, thanks to a wizard-driven interface

7. Piwik PRO: Piwik PRO can either be used as a local or cloud solution. To use locally, Piwik PRO can be downloaded, installed and used by anyone—but those in medium to large-sized businesses will see the most benefit in the solution’s powerful capability.
Features:
a) Open source
b) Integration with popular CMS platforms
c) Synchronous and asynchronous HTML tags
d) No data limits
Piwik PRO pays a lot of attention to security and privacy, which can be a good alternative to GTM where the topic of data security gets a little murkier. They also provide a large library of templates for tags and variables to simplify your implementation process.
8. IBM DDX: Included with the IBM Digital Marketing Optimization suite, DDX has similar capabilities as the other TMSs mentioned in this post. DDX also allows users to syndicate real-time digital intelligence via the “gold tag” API.
Features:
a. Intuitive user interface to ensure accuracy and consistency
b. Capabilities such as versioning and rollback
c. User-defined tag deployment and scheduling
d. Visual overlay of the website via the tag bar solution

9. Yottaa: While Yottaa does not classify themselves as a tag management platform, they perform the same function as most TMSs. Yottaa’s target audience is eCommerce companies, with one of their principal objectives to give a single point of control for third-party technologies to increase page load times.
Features:
a) Automated and accelerated rendering of dynamic and static content
b) The ability to manage the order and execution of first- and third-party technology
c) Cross-device optimization of mobile and desktop properties
d) Dynamic optimization based on location, device type, network connection and more

Besides if you do have any questions give me a call: https://clarity.fm/joy-brotonath