@CaliaMoko If you start thinking less about "turning the echoes down" and more about "sending less signal to the echoes effect" you may start getting on the right lines
For an "insert effect" there is likely to be a Wet/Dry control, often shown as a % - 100% is usually all wet, so you hear only the echoes and no dry signal (which sometimes catches people out as it can sound like your audio is not lined up correctly as you on,y hear the delayed audio)
In this case if you want to "turn the echo down" then you simply adjust the wet/dry balance to have more dry signal Anne less echo (i.e. a lower %, where zero only gives you a dry signal and no echo at all
It may be possible to automate this control so you can adjust it in different parts of the track
The send method does have a crucial difference, which may be catching you out...
Essentially you have the echo on a separate track, set to 100% wet
You then adjust the amount of dry signal going to the track with the echo on it using the send control
However, it is important to understand the "routing" of your channel strip in Reaper as although the order usually flows from top to bottom most DAWs allow you to put your SEND either side of your fader for that channel - either before (pre fader) or after (post fader)
This can often catch people out but if you stop and think it makes sense...
If you set your send pre-fader then the SEND control adjusts the amount of signal going to the echo - so if you dragged your fader all the way down you will STILL be sending signal from that track to the echo
If you set your send post-fader then the SEND control AND the fader will adjust the amount of dry signal going to the echo - so if when mixing you increase the volume of that track using the fader you will also increase the amount of signal going to the SEND, which is also then passed to the echoe
If you are using a SEND effect and not getting the behaviour you expect then I would investigate whether your sends are pre or post fader