Classica vs Lusso: less is more. I think it's a very personal choice, with good arguments for both.
I chose Classica, but not for budget reasons - I want as close as poss to a great-looking 60s sport car as I can get, with the modern additions of reliability and weatherproofing. An updated MGB if you like.
Engineering wise (for me): simple = better. The less modern tech, the fewer the gremlins in 10 years time. I'd love to ditch the push start and have a simple flat metal key.
Maybe one thing to consider in Classic vs Lusso - how long do you intend to keep it?
I am intending to keep mine indefinitely as I suspect the (new) 124 will still be a looker in 5-10-20 years, and high volume production numbers suggests long-term parts availability, especially since some parts are MX-5 shared. Think MGB again - simple, affordable, popular, supported, and still visible on the roads. I want mine to be a future classic, so the satnav/tablet was a no-no (nothing gives car age away like the satnav - look in any 10 or even 5-year-old car).
Ditto leather - modern leathers (I think they have plastic coatings?) tend to look a bit ropey & creased after a few years, especially the bolsters, and I think cloth feels so much nicer - warm in winter, cool in summer - the opposite of leather. **
Wheels - hmm - well - the bigger ones DO look the part, but the smaller Classica ones give me so much more tyre cushioning.
Just one more thing - I prefer the painted windscreen surround (Classica) to the chrome one (Lusso). I guess that's a personal thing again - in the 60s Bridget Bardot could have slapped on earrings & other bling, but, being already beautiful - she didn't need them - less is more!
** I've never quite been able to see how leather became synonymous with luxury. To this day the Royal Family have the leather removed from the rear of their cars and replaced with cloth - the current State Bentley is an example. The reasoning (comfort aside) is that leather was originally reserved for the chauffeur who sat up front in the rain - those in the covered rear didn't require their seats to be weatherproof. (Okay, history lesson over).