Ostarine is the only one that you'd find that some people will say you can use during PCT. I would advise against that personally. S23 is supposed to be stronger than S4, but without the vision sides. With this in mind, it's also supposed to be very suppressive to natural test. Another one like trest where it's being considered as a male contraceptive. So no, none of those will be good ideas to bridge with as you're really just staying on cycle.
Mk677 is okay to use, as it's not a SARM, but a growth hormone secretagogue. GW501516 is also fine, as it also is not a SARM, but rather a Peroxisome proliferator-activated receptor beta/delta agonist, or a PPAR drug for short.