It's hard to say which sensor specifically would most suit OM lenses IMHO as pretty well any A7 version will produce excellent results with vintage glass (any vintage glass!) But I can say that I now shoot with an A7s (the original one) which in camera years is pretty old and love how it functions. Especially its ultra high ISO performance (not that I need to go ultra high often) and its associated excellent dynamic range. It is really the dynamic range I want. As I do a lot of street shooting the threat of blown highlights was my nemesis. But now with the A7s shooting RAW files and especially if I deliberately under expose files by up to one stop in high contrast situations it is now never an issue. And with this camera sensor, shadow detail can be recovered easily, as well as highlight detail - it really is very, very good. Also the A7s series only has a 12 megapixel sensor. This helps quite a lot in terms of processing "grunt" needed and the amount of storage required on disk.
BTW as to adapters. I now tend to buy only K & F concept adapters which are extremely well made and quite inexpensive (compared to the top of the range ones). One trick I have recently learned too, is because I like to shoot multiple lens types / lens marques on different body types - M4/3, Sony A, and Fujifilm bodies I now stack adapters by buying a Leica M adapter for each body type I use, then mate this with a lens type adapter to Leica M adapter. This means that if I wish to use 5 different lens types on 3 different body types I only need one Leica M lens adapter for each body type and one adapter for each lens type to convert each lens type to Leica M. This means buying fewer adapters. Not an issue if you only plan to shoot OM glass on Sony bodies but it does give a flexible arrangement which is future proof. As each body now has a standard Leica M mount instead of its own proprietary mount it is much easier to use with different lens makes.