Most TLRs are going to be a huge pain for using filters - a lot of them use bayonet mounts for their filters, and any filter is going to block the viewing lens (as well as issues with placement). Additionally, aside from the Mamiya system and the rare Tele/Wide Rolleis (both of which are significantly out of your budget), they all have standard lenses - which might not be useful for landscape work.
There's no problem at all with screw in filters. For black and white work, a TLR is better than an SLR in that respect because fitting a red filter doesn't make you see red through the viewfinder. My C330 takes filters just slightly smaller than the 49mm size of the OM system; and I have a complete (for my purposes) set of screw in filters in 49mm size which I can use with a stepping ring.
There's only a problem with placement if you want to use graduated filters; and in over 50 years of photography I've never felt any need to use one. OK, I have a tobacco graduated one from the 1970s; but everyone used one of them in those days.
An awful lot of landscape photography has been done with the standard lens, and to all intents and purposes it's the only lens I use. The problem has only really arisen (I think) because of the relatively modern line of reasoning that runs thus:
1. You must have a sense of depth in a landscape photograph (which isn't actually true).
2. You achieve a sense of depth by incorporating a large foreground object (which isn't the only way of indicating depth).
3. Because you've had to move in really really close to a big rock, you need a wide angle lens to show any of the scenery that you wanted to photograph in the first place (and, as a by product render it vanishingly small in the frame).
Therefore: you must use a wide angle lens for landscape photography.
If you "see" landscapes this way, then you do. Personally, I don't and prefer the perspective I get from a standard lens. In the last 10 years or so, I think I've used a shorter than standard focal length twice, and a longer than standard 4 times. SO it's a mtter of personal taste and how you express yourself.