Williams is the closest thing to post war without being Post War, but not always "great" runners early on when they first expanded from tin; that took a few years. The later Williams is spectacular. Even Williams by Bachmann has the PW look, great prices, and very simple electronics.
I am not a big fan of the later diesel pulmor, and really had bad luck with dual fields. Only the "one piece" motors and steamers are really worth a poop imo, Pittman aren't THAT great, but they are very comparable to the later Pulmor. ( I have a tmcc Pulmor E-33 Virginian rectifier too, that is the best "diesel" Pulmor I've ever owned. Very smooth, and very quiet, not a lick of gear growling, just deep magnetic field growls.
I would still hunt for PW, and Pulmore, but can motors have grown on me some too. Don't be quick to put all your eggs in one basket.... I see opportunity for low cost repairs and consider them closely when cheap. Especially new things in fine mechanical shape, with a cooked motor, e-unit, or sounds. Can motors are missing certain nuances, sure; but they perform soooo smooth that you have to give them a nod of respect. The ones with simple electronics are very servicable at a reasonable price. And moving to simpler boards to run the fancy ones is possible too. It's just sounds and (especially) command that gets things complicated and pricey.
I have also come to realise I seldom back up, so wiring in a $2 bridge rectifier for fwd only on a can motor, in place of a burnt reverse board, seems like a perfectly reasonable "whenever, if ever" repair option to me. An e-unit is no easier to swap around than a board, or rectifier, and the wires are actually easier to solder on a board or rectifier, and some engine boards just have plugs. Taking my newer Berksihire apart for the first time, I had to marvel at how easy it was to work on compared to PW. Four screws and lift! No rods or linkage, etc, needed to be touched. I know that isn't always the case, but it has me looking twice now.
Your letting those electric boards scare you and it shouldn't. A transistor is just a tiny relay. Resistors just got smaller, rectifiers are no longer discs or the size of a tender, and they call them diodes. Chips are just fancy combinations of them all, with a few clocks and counters thrown in here and there for fun That said, simple electronics are ok, but I have no want for all the sounds and control boards either. Mine new ones are gifts, and usually run with the volume low or off. Chuff gets old fast some days.
One thing I really like is the cycling sounds on a parked tender. Having it on a siding also gives me a bell or two bells! ...that's the modern sound options I do like
K-line had similar "conventional electronics" engines you might want to consider too. MTH? RMT?
Someone pointed out once if you took a can motor engine and added an e-unit coil or buzzy relay, you'd likely never notice anything but the smoothness. Funny to admit, but I think it sounded about right now