I’ve been using LSPosed + WAEnhancer on my daily driver for quite a while now, and I haven’t experienced any stability issues. As long as you install reputable modules and don’t go overboard with tweaks, it’s generally very stable.
For WhatsApp call recording specifically, WAEnhancer is probably the best option available on a rooted phone. It also adds a lot of other useful WhatsApp features, so it’s worth trying even if call recording is your main goal.
If you’re worried about stability, make a full backup first. That way, you can always roll back if something doesn’t work as expected. In my experience though, LSPosed itself hasn’t caused any problems.