25mg 4-AcO-DMT is perfect for me too, at least with fumarate. I tend to take quite high doses of it (35mg+) but 20-25mg is the nicer more relaxed range, still strong in the case of 25mg, but not overwhelming.
Back to MXE though, if it were me personally I'd try 15mg for that. 15mg sublingual was my first dose with MXE and it was very relaxed, euphoric, but stimulating too - just not overwhelmingly so. There's a light hint at the dissociation but nothing major at this dose for me, it was more a relaxed booster than anything else. Lower doses would work too but they're very subtle so might not be satisfying at a party. 20-25mg wouldn't be too much to take, but you would experience dissociation. I'd definitely avoid going over 25mg sublingual though, particularly your first time.
I'd avoid the whole redosing thing personally unless you want it to last ages. I find unless I redose immediately after I swallow any remnants of the first sublingual dose - or the redose is much bigger, it doesn't really increase the peak, just prolongs the overall duration, and increases the stimulation - which can last for several hours after the main experience is over. In my experience that has led to at least two nights of no sleep.