yes more than one is good IMHO
definitely having one before ERAS or interviews to get a subI LOR in your field is a good idea to show you are prepared to go on as an intern IMHO
I was told this by my advisor that a subI in time for ERAS was essentially expected, remember, I am reporting heresy here, the only fact I am presenting is that a school advisor said someting to me
you could also do an ICU rotation as your second subI, it would be tough but good prep IMHO
one of my cointerns did like 4 subIs 4th year (too many? I dunno) but they looked like a rockstar beast and it seemed to help them a lot, especially efficiency
many would say this is overkill and enjoy 4th yr take easy stuff, I dunno I was weak and in hindsight wish I had done more to be prepared
could it harm you? of course, just like failing a test
however that doesn't you should just opt out
when I think it is important to a good match to have done one in time for a a grade/comments/LOR that comes from it to be available to programs
as you mention you need to do well of course
an away rotation could be iffy as it can be hard to adjust sometimes and systems issues could bog you down
IMHO then it would be good to do both your subIs at home if you think you would be more successful than an away which is always taking a chance
of course there is an advantage to an away in that it shows flexibility and adaptation which you will need going to a new program from what I've been told
TLDR:
I think more than one subI beneficial and getting grade/LOR from it in time for ERAS is essential IMHO, based on advising I received
it is tough to say if an away will hurt or help