The Wiki over at LUF is a gold mine for information about lenses with loads of threads linked under each lens. This is what I used when I read up on the M system before moving from EOS. RFF is also a great resource for information with a somewhat less stroppy attitude (imho) (no offence intended, I hasten to add). There are lots of Bessa users at RFF and a special sub-forum for it, I believe. I use an M4, an M6 and a Leica II(D) so can only speak about them. They're all great, and the II(D) is particularly pleasant (and unusual) to use.
I have two modern APO Aspherical lenses and a few very old screwmount lenses. It is definitely right not to exclude older (pre-asph) lenses. For me whichever I will use depends on what I feel like using at any given moment together with what I'll be photographing. Softer, older lenses render portraits very nicely.
For instance, this is a shot with my 1950 5cm Summitar using my 1931 II(D). Pretty smooth highlights, at least some of them.
Reading at 20:05 | Flickr
This is a shot from my 50 Summilux Asph which also has smooth highlights.
Hello. Kitty. Singapore 2012
Actually a black and white may be better to compare with the Summitar. Again with the Summilux:
Lonely in the subway. Singapore. 2012 | Flickr
So how the highlights render will depend a lot on the light and the type of background, messy or not etc. It is possible to get the asph lenses to render smoothly and pre-asph lenses to render with christmas light-like disks. As for contrast, yes modern lenses are pretty/very contrasty. I like it sometimes and sometimes I like the softer rendering of older glass.
There's a pretty amazing thread over at LUF - The view through older glass - which includes photos from an amazing array of non-modern lenses (the condition for posting images there is that the lens used was not a current lens). Highly recommended for inspiration!
Hope it helps some. Write back with questions if you like.