Philippines provides a 21-day visa on arrival for most countries. The official website has more information: https://evisa.gov.ph/
Philippines is considered very safe if you are in tourist regions. If you are visiting more remote regions, make sure to read up before hand as there can be some places that are more dangerous.
Really depends on where you are but it is cheaper compared to western places. End of the day, it’s also going to be all about how you travel. You can do it very expensive and choose fancy restaurants and hotels or you can choose street food and budget guesthouses.
Credit card adoption is picking up but you will usually be met with extra surcharges of 3-5% so cash is still king.