I know you've received some great advice already, but, I thought I'd throw my two cents in there anyway. I'm about to have four kids (due the 27th) two of which are a 3 year old girl and a 1 year old boy.
I don't think I'm a great housekeeper and I'm okay with that because I really do believe that this is a crazy time in our household and that sometimes, the only thing I can do is to just let some things be dirty for a while and trust myself to find an okay time to do it.
I have struggled with the same questions you have ever since I got married and started having kids. The conclusion I've come to is that ultimately there's a lot of personal preference involved in these things (what you can tolerate, live with, what you have patience for, what your priorities are) and that in some things, there are no rules! When you have a 3 yo and a 1 yo, schedules get changed all the time. Some things have to be flexible. Some things won't be black and white with a strict set of rules.
Kids go through phases and so do moms! Today, I've already swept and vacuumed the kitchen and dining room 3 times. Normally, I wouldn't ever do this but the floor was especially dirty and I had the energy to do it. Most other days, I would have waited till after dinner.
Most days, even though I know it's possible, I'm not a fan of multi-tasking. I'll take advantage of a few moments here and there of the kids playing on their own to get stuff done, but, if it's just not working out, I'm okay with leaving the mess and just paying attention to the kids. Personally, I find that less stressful even though the mess is still bothersome. I have to force myself to do it though!
There are certain things I just won't do if my 1 yo is around. My husband has a higher tolerance for certain things like loading and unloading the dishwasher with our 1 yo. I wait until he's asleep or know he'll be out of the kitchen long enough for me to get it done. I just don't care to deal with the struggle, even though I know it's possible.
My dining area and kitchen floors are small. They rarely are actually mopped. I have a set of old rags that I use to spot clean the worst spills and am okay with it not being as clean as it could be.
Right now, I prefer to save up the laundry and fold a few loads in the evening while I watch TV or a movie. I put loads in when I happen to think about it and I store the clean laundry in my room away from the kids where it'll stay clean until I can fold it.
I used to have a higher tolerance for dirty dishes, but, now that we have a nice dishwasher, that's one thing I can't get behind on. Even still, I save up the breakfast and lunch dishes and don't load or clean until after lunch when the kids are asleep and otherwise occupied (I only put food away and dirty dishes in the sink after breakfast).
Someday, I will have more school age children than toddlers and that's when I think less-flexible schedules will have a place in my house. Until then, I try to have a running game plan in my head, take one day at a time, and keep an eye on the week as a whole. But, I also try to be at peace with the fact that sometimes, my toddlers are going to be the deciding factor of the day and that I'm going to be okay if the house is dirty for another day. There's a lot of reminding and pep talks going on in my head, but, for now, it's getting me through.
Good luck to you and try to enjoy this super adorable time with your toddlers (one of the things I have to remind myself of all the time!).