Are they allowed for speedrun submissions since I travel

It depends on the game, some leaderboards only allow runs from specific emulators while others might allow it.

It depends on the game but browser based emulators are pretty bad and most likely won't offer the tools all leaderboards (should) require for verification. Such as frame count, input reader, etc.

I've played a lot of games on emulator, and so far the only boards that I've noticed that allow browser emulators are for MSDOS, and even then it's game-specific. If you have any questions about a specific game, message the moderators. You also have the ability to run emulators on mobile devices, and while most mobile emulators are banned for boards, I've noticed that Atari 2600 boards generally allow them, as well as some NES boards.