New to this, but my current plan is to mostly do 18:6 and 20:4 but throw in one 42 hr fast weekly. I have tried this schedule for 3 weeks now, made it thru the 42 hr fast 2 out of 3 times (hit 28 hrs the other time). I like having the various in fasting times from day to day and working with my schedule.
I lost 60lb in 18 weeks doing 16:8 with a 3 day fast (actually 88hr) every other week. Have been maintaining at target wt now for 5mo doing 16:8 with 1 or 2 fast days (40hr) each month just for good measure. The longer fasts were somewhat difficult but trained me well for long term IF now it is really easy. Even the occasional fast days are not that bad I actually kind of look forward to them. It is actually strange to type this thinking back to when I started the last April I had never fasted before. I guess it just worked out well for me.
There is no way to overdo IF in itself, in my opinion. The health benefits are staggering and downsides have not been identified.
However, if you lift weights regularly and fail to respect that recovery takes much longer on a calorie deficit, then you can easily wreck yourself in ways that will prevent you from lifting for months/years. It can happen rather suddenly, and the warning signs are not always easy to see until it is too late.
If you do lift a lot, perhaps head over to r/leangains instead. They specialize in IF + lifting.