I think the GOP knows they are going to get one bite at this apple, and they are taking advantage of it. Hello tax reform and good bye NN.
The ones that are on shaky ground are those in areas that previously voted Republican primarily for economic rather than social reasons (i.e. for the sake of low taxes, not because they wanted to ban abortion etc), and are now flipping to blue because Republican social policies became intolerable. This is many suburban districts. And Republicans there are listening; for example, in my district (WA-8), Dave Reichert voted against AHCA.
The catch is, Republicans in those districts know that even if they pander to the new electorate somewhat, there are still enough reasons why their Democrat opponent will likely get their vote. They'd basically need to be liberal on everything except taxes (and given the nature of the tax proposal that Republicans unveiled, not even on that, since it hurts the suburban mid/high-middle class dwellers most!), at which point they might as well just switch parties. So you see a bunch of guys saying they won't run for re-election at all, and then they treat their remaining term as a means to squeeze the few last things in while they can.
If you mean who I'd vote for, it would be the Dem candidate, no question. The parties are far enough now that I don't foresee a situation where a Republican candidate would be more closely aligned with me on the issues than a Democrat, even a particularly disagreeable one. But, more importantly and urgently, I think that this administration must have some counterbalance in the Congress to check it. But this is a moot question, anyway, because I'm not a citizen and cannot vote.
They won't get money from their big $$$ donors if they don't pass the tax cut bill. They won't survive a primary if they're seen as being 'soft' on the ACA by the true believers in their party.
They don't have any idea how they're going to make it through the general election, but that's a fight for another day. They have other priorities first.