Gw, mk677, ostarine and S4 I assume would be about as good as it gets. Gw and mk are not sarms and has 0 effect on shutdown and can be used during cycle, during pct and after pct.
I'm not fully on board with time on time off with sarms since they have about 0 androgenic sides, they have minimal shutdown and cholesterol and blood pressure shouldn't even be affected not to mention you're probably a good candidate for trt at your age. this being said since we're talking about products that in theory are about as safe as it gets we don't have the full information what they could do in the long run even if it looks beyond promising so take that for what it is. My advice would be to take a blood test and see for yourself exactly how it affected your production cause some people say it was barely noticible while others claim complete shutdown. I don't believe a legit Sarm would cause complete shutdown after a few weeks but that's not proof that's just my own belief.