Westone ER15's for me as well. Been wearing them since the mid 90's and been thru many pairs. The last custom molds have been the best because they are clear, supple, & still fit perfectly because they don't shrink over time.I have been using custom plugs from an ear doctor, same as you. I’m on my second set. I believe both sets were made by Etymotic but the second set may be Westone. I can’t remember. Anyway, they’re more or less the same.
Mine initially came with 20dB filters which I found too muted. I changed them out for 15dB and that’s what I’ve used ever since (about 20 years now). They also make 9dB but those mostly only cut mids and treble and I couldn’t get used to them.
All in all, I think I hear more clearly with the 15dB filters than I do with no plugs in. They eliminate a lot of sonic clutter but they did take a few weeks to get used to.
I’m actually about ready to replace my current set. They’re starting to crack a little bit and they don’t fit as well as when they were new.