I think ETH is a very pragmatic manager, and will look at who is available, and who the opposition is, and adjust the game plan accordingly. Frimpong and Timber give completely different options, as Frimpong allows us to have an attacking RB to support the RW in overlaps, and potentially overload on that side. Timber is really a centreback, but could be used similarly to Shaw as a RB / RCB cover, so he could play with Shaw Martinez Varane Timber which is very solid defensively, and the two ex-Ajax guys give good ball progression also.
I would be happy with either of those two, or both. However, it looks like we may be bringing in Kim Min-Jae, so I doubt we will be signing three new defenders, and it looks like Frimpong will be the new RB. Maybe Timber has missed his chance and he will have to wait for Varane to retire to come in as the new RCB / RB. I don't know Vanderson well enough to comment.
Next season our defence could look like:
Shaw / Martinez / Varane / Frimpong /
Malacia Lindelof Kim Min-jae AWB