[We've discussed this a little on the Discord too.]

I believe in spacing with both thumbs as appropriate. That said, I do use the right thumb most of the time. I also believe in using both Shift keys, if that's relevant. But maybe it's too ambitious, hehe.

If you get tired from using the Caps Backspace, maybe it's because you're mashing it? Also, maybe it is because you're new at Colemak. I've heard of people complaining about Backspace fatigue when starting to learn Colemak but then it subsides as they type more confidently with less errors.

I try to delete whole words as much as possible, as explained in my Amphetype topic. That way, I won't be mashing the Back key which is good because I think same-finger n-grams are quite straining in the long run. I use the Caps key as my Extend modifier and hit Caps+T+O (= Ctrl+Back) to delete whole words.

PKL_eD has this functionality, but by now I think you've learned that. ^_^