All native gCOTI holders are eligible to vote, regardless of the amount of gCOTI held in the wallet or locked in treasury deposits. Not only the gCOTI held in your wallet but also your gCOTI deposited in the treasury will count. A snapshot identifying your voting power (= the total amount of gCOTI you own) is taken randomly during the 24 hours after the voting closes.
The proposal with the most gCOTI voting power, i.e. the proposal that is voted for with the highest amount of gCOTI (not the highest number of votes) passes. You can vote more than once and by that change your vote. Only your latest vote will count.
The governance page is being reworked for COTI V2 right now.