CitiPremier miles is a good general card as the miles don't expire. However for me, I am using OCBC 90N, also miles don't expire and you can change in blocks of 1,000 miles. Only downside is that it's only for Krisflyer miles and no lounge benefits. If you have an UOB One account, you should have at least 1 UOB CC also (miles/cashback it's up to you). Reason being is that if you can meet min. $500 spend per month, you would be able to hit your UOB One account criteria (Assuming you have 3 GIRO or salary credit to it). Also, UOB One has a tie up with Grab, where you can get up to 10% rebate on it. This is insane. I only just got to know of how good a deal it was! On your last point to be loyal to one bank, no not really, you should select the credit card which suits you!

HSBC advance does. You can try doing it. Some hotels will issue you a GIRO form and you will have to write your card details and CCV etc. This way may work because they need the details but not the physcial card. You can ask the hotel guest services about it

Maxigain is tagged to another component which is the 1mth sibor. Unless it is poised to goes up, if not ocbc is offering $50 for every $5k deposit and will need to lock in for 7 months.

UOB One's general rebate is really hard to fully take advantage of - for the headline "up to 5% on everything" - the key part is UP TO you need to get exactly $2k per month for 3 months to get the 5%. Any less and you get lower tiers (3.3% or worse), even any higher you won't get more cashback so starts to effectively be lower than 5%. Given your spend amount - you could qualify for lowest tier and if you are confident that you could put through $500 per month consistently then maybe worth considering otherwise I would give it a pass.

I would say both have its own strength and weakness. For DBS Multiplier, you can hit actually hit salary crediting, credit card spending and investment category. If you were to do a SSB ladder, you can get the investment category part of the crediting dividends as long as they don't change the criteria. All you need to do is to buy 6 months of SSBs consecutively and make sure your CDP is connected to DBS/POSB account. This way, after the 6 months of buying SSBs, you will receive SSBs interest every month for 10 years which will count as investment category under DBS multiplier. SSB minimum amount is $500 every time so it will take you at least $3,000 but of course, you can put more if you want to. The more transactions you have with DBS, the more interest you get. But for me their credit card doesn't really suit me, they have slightly higher minimum monthly balance, an additional step which is the SSB ladder and I don't have that much transactions in the first place. For UOB one, their credit card gives cashback for most stuff although you have to spend at least $500. (not very hard if have fixed expenses that UOB one give cashback.) Their EIR or effective interest rate is only 2.44% if you have 75k in the UOB one account. They also allow 3 giro transactions instead of salary credit so a bit different as well which means if you plan to keep a big amount of money with the banks you can do both DBS multiplier and UOB one at the same time with a single salary crediting. The headache part is if you don't hit $500 for a single time, you won't get the interest and you won't get the cashback for the quarter. Overall, just choose the accounts and credit cards that suit your need the most.

I would excuse myself from this topic as i am not a subject matter expert on this.

Higher returns tend to run in line with higher risk. The thing you need to ask yourself is how much of a risk appetite you can stomach before you need to cut losses. Generally speaking the safer choices would run the gamut of fixed deposits, higher yielding bank accounts like cimb fast saver and citibank's maxi gain, structured deposits, Singapore savings bonds, ABF Singapore bond index fund (through posb invest saver). Robo advisory portfolio with low risk profiles may also fit in here. Higher risk choices would be straight stock investing, robo advisory portfolio with higher risk profiles, equity Etfs and options portfolio. Typical returns range from about 4% to 40+% or more a year. For non managed portfolios, I'd suggest you find a mentor to teach you to shortcut the learning process. Saves money in the long run and you will be able to achieve your goals much faster. Just ensure there's a track record for the programme. Hope this helps

Have a sufficient balance in your savings account. E.g. Having the min balance + some spare cash to use. Then the rest you can put into SSB. If you can hit the conditions for High(e.g. 3%) interest, you can consider just putting in the savings account itself.

I work around this issue using other means to save. First I use BOC credit card for its cash back, but due to no salary credit bonus, I stuck with OCBC frank giving me 0.2%, and usually keep the bulk in SSB or buy stocks/REITS. If I do need emergency funds, I can swipe my credit card first then redeem my SSB to pay the bills. WIth this general strategy, my bank account does not have too much cash.