So I finished an NCR playthrough where I had BOS paladins supporting me at the dam, and this time I'm going for the yes man/independent route.

Is there any way to get the BOS to support me like they did the NCR, and does it matter which elder I keep in power?

No you can't get them to support you but in the Yes Man path you can decided to ignore any minor faction you want. You could get them to ally with the NCR again. When done right you should only have to fight NCR troopers while siding with the legion.

So for the yes man path, does it at all matter which elder is in power?

No it doesn't you can choose either to ignore them, destroy them. If you want them to help the NCR its no different then before.
I still advise keeping McNamara as his joining quest doesn't step on any toes like Hardin's