Better on a 848 than a 748 for sure, but that's a bit like saying cocaine is better for u than heroin! I would think that it's do-able though for the odd ride, the pegs are set far enough down.
Welcome!! You'll find some good/cherished 748's out there for sure but as many have said older bikes need more TLC and servicing costs will be your biggest issue. 749 or even a 848 would be a better shout, although I do feel as the testastretta engines have evolved they've lost some of their character... but undeniably a better engine and reliability. Tough call.
Welcome to the forum. I loved my 748, but I would work on it myself. You have to love a Ducati. For a first one, if you're on a budget, get the newest you can. If you could stretch to the 848 I would do. The last thing I'd want as a Ducati fan is someone buying an old one, throwing money at the dealer all the time and hating the whole experience of ownership. I've had £1K+ bills just for labour on a 996, but I bought cheap. You pay one way or the other. 848 much better from what I read.
Welcome. Never owned a 748 or 848 so not qualified, but you are clearly moving on to Ducatis because you have fallen in love with them, so buy the one that's object of your affection.