Does this reinforcement bar require the bumper to be removed for installation?

Yes. The bar installs from behind, so you'll need to remove the front bumper cover to access the mounting points. Once off, the bar bolts directly to the existing frame locations underneath.

Will this interfere with bumper sensors or parking assist systems?

The reinforcement bar sits deep enough that it won't block sensor coverage. If your Highlander has parking sensors in the lower bumper, they'll function normally once you reinstall the cover.

Can I paint this before installation, or should I wait until it's bolted in place?

Paint after installation. The bar sits hidden behind the bumper, so prep and finish aren't critical—but test-fit it first to make sure the mounting is solid before committing to any prep work.