My choice would be Apache JMeter, It's free and opensource plus it comes with lots of plugins and extendability. Apache JMeter needs a small amount of a learning curve and a basic understanding of Network, Protocols (TCP/IP ports, HTTP(S) and REST/SOAP, etc.) for initial setup. But it doesn't require programming skills. it has a nice record and playback option. You can still carry on without the developer skillset if you follow these steps.
- Take backup.
- Start recording and interact with the application.
- stop recording and save the test case. This will give you your test-bed, after this, after these steps, every time just do Restore from backup and then Playback and observer results.
If you have longer recordings then an understanding of how to modify the recorded scripts will come handy.
For some of the advanced features such as Configuring variables, implementing loops, throttling adding think time, and automating test scaling to the number of users will require good planning of test scenarios and a Developer experience but this is true for any tool (even loader.io)