Which part of the custom framerate part were you having trouble with? Within Premiere or exporting? Exporting to h264, you cannot do custom framerates. Only industry standard framerates like 23.98, 24, 29.97 etc. So I choose 24. Like I said, the Premiere workaround is a little janky and I can try to give a better explanation if that's where you're stumbling.
I chose VBR 2-pass because it's slightly better on compression than 1-pass VBR and is better on size than CBR since it gives more or less data to frames depending on their complexity. BUT you sacrifice rendering time as it's double length. Not a huge deal to me as I'm normally exporting out 3-5 min films. I still use the other two settings depending on time/quality needs. If it's a quick thing or I just want to preview it or pass to a client for approval, I might do CBR because it's faster.
Also not sure where you'll be uploading but I'd actually recommend always exporting out a ProRes master edit file THEN from that creating your small versions as your needs require. Sites like Facebook (I think), Vimeo and YouTube all will accept ProRes files for upload so I figure why not give them the best you can before they smash it with their own flavor of compression. Also this depends on your membership level at Vimeo and how much space you can upload per week.
Then if you want a small version for putting on a flash drive or something, you can convert that master ProRes file in Adobe Media Encoder and it will be much much quicker than re-exporting from Premiere with your color edits.