I was thinking of encoding my collection yesterday. I couldn't decide between -V 0 and -abr 280, so I thought I could have the best of both by restricting -V 0 with the -b and -B switches more specific -b 256 -B 320. Should I just leave -V 0 as it is?

All that does is 'shift bitrate distribution'. Parts than need more 320k frames will get less etc . No point in VBR then.

I would stick to plain ABR if you want those higher bitrates. --abr 280 or --abr 287 -h

I'm trying out --abr 287 -h now. Bitrates are around 266 kbps, is this ok?

yes. Lame 3.98 has more restricted bit reservior. Bitrate will go much higher if needed.

Thanks for the advice,-abr 287 seems to be the sweet spot going higher than that gets close to 310 kbps on some tracks.

An ABR setting like --abr 287 -h is a good setting IMO for the very quality aware user even with rare problematic cases.
Just a remark (my usual one for this situation):
As with such a setting there are many 320 kbps frames, applying the lossless and fast mp3packer procedure after encoding can save a significant amount of bitrate.
And you don't have the restriction to stay at 287 kbps. Bitrate penalty doesn't grow inappropriately in case you decide to go a bit higher with bitrate.