“The different minhogim between other chassidim and chabad”
1’s point was that Chassidim might claim they’re more authentically following the older mesorah than Litvaks. Examples of this would include yotzros, late minchah (even the no tachanun part is based in the Rema), M”A zmanim, R. Tam’s tzeis, and several parts of davening that most modern Litvaks skip al pi haGra.
As for Chabad-specific things, people have already mentioned several. There are many Chabad minhagim which everyone is fine with, but those aren’t the ones they are known for. They’re known for the ones like eating before shachris, no seudah shlishis, davening late, etc.
“And why only chasam sofar or rama?”
That was lav davka. Any Ashkenaz sect should not ignore the Rema. The Chasam Sofer is a specific example because almost all Chassidim regard him very highly, while Chabad, on the other hand, will brazenly and erroneously call him a misnaged. Just an example of the deep divide between Chabad and Chassidim.