do I still earn rewards at 100% upvote but with 60% voting power?

Yes, if you are at 60% voting power and vote 100% it's as if you had voted 60% at 100% voting power. It's all in the rshares. Considering you're SP is low and you want to make sure to reach 0.001 SP curation rewards minimum on each vote I'd suggest to let your voting power be as high as possible.