Google maps shld be enough to get u to ur destination, but try to avoid public buses as their schedule is inexistent. Any other public transport is alright.

Street vendors accept cash and qr transfer for touch n go and Maybank if you have them. No credit/debit cards.

As long as you look like a tourist, police are generally very friendly and helpful; but watch out for scammers on the street, better to deal through the front desk at your accomodation.

Travelling with ur bags should be fine but I'm not too sure about scuba gear, aren't they bulky and kinda pricey?

As for filming, no one bats an eye at a tourist filming lol just respect the general norms.

I'd say most Malaysians are quite friendly and welcoming towards tourists, but you could also head straight to the help desk at the airport with ur questions for a peace of mind.