Hi there and apologies if this is the wrong area to ask about this!

I am traveling to the US tonight. I hold both British and Canadian passports and I am currently in Malaysia for holiday. I traveled into Malaysia with a British passport and applied for a Canadian passport here.

I wish to travel to the US using my Canadian passport as it allows me not to have booked an onward flight along with other benefits. However I'm a little confused on a few details:

Would it be OK for me to check in using my Canadian passport, then hand my British passport to Malaysian emigration? I just worry that they will see I have a different passport number on my boarding pass.

Also when I arrive in the US I am concerned that on my Canadian passport it will not have any travel information as I obtained it during my stay in Malaysia and they will only have processed my British one when leaving Malaysia. To further complicate things I have previously visited the US on my British passport. Would it be best for me to be completely straightforward with the immigration officer in the US and show them both passports right away?

If anyone has any ideas about these worries I would very much appreciate it. Thank you!