I've recently switched to Swiftkey because I'm having some problems with Gboard. The one major thing I miss from that, however, is its wonderfully simple and intuitive 'gesture delete' function. You should really, REALLY check it out to see why it's so much better than just pressing and holding the del key and hoping you can release it in time to avoid deleting more than you wanted to. This is particularly important on a system like Android that doesn't offer any ctrl-z type undo options. All you do is swipe left off the del key until the text you want to delete is highlighted, then release to perform the delete. If you swipe too far you just have to slide back towards the del key a bit first. Simple!
I also find it mightily frustrating that the last word entered by flow typing can't be deleted with a single tap on the del key. That's how every other 'swipe' type keyboard app I've tried works and it seems pretty obvious to me it's how it should be. I realize this has been asked before and rejected, but I'd urge you to reconsider and at least make it an option.