“I’m constantly told that I have no right to disagree “
Maybe you don’t. But your rav does!
‘And if I dare to follow a rav who offers a lenient opinion, all I hear is “is your rav greater than Gadol X?”‘
The people who say that need to consider two things:
(1) Your rav may indeed be greater than Gadol X, just not as well known.
(2) Gadol X might well be equally lenient in your particular situation.
If you are following your own rav everyone else must accept that.