You CAN cut flats to fit, but you have to be very careful. The key is to put at least a 90º bend in the string before you cut it. The bend helps keep the windings in place. Then you have to carefully put the string into the hole in the machine without unraveling the winding. It's a pain and pretty much not needed if you can buy strings sized correctly for your bass. Also it depends on the size of the tuning machines. Large rollers like Fender, Lakland, Music Man, etc. use on their basses will be OK. Smaller rollers like the Schallers and Gotohs used on Guild Pilot basses would be a bad choice for cut flats.
As to the original question- I've never used Chromes, but the consensus on Talk Bass is that they're brighter flats than most. My favorite flats are GHS Precision Flats in the roughly 45-105 gauge set (I don't know the exact gauges because it's been so long since I put them on the Precisions- at least five years). I like them because they have a definite note in them- I play bass, not a kick drum and to fulfill the bass' role you simply MUST hear a precise and definite note. I've used a couple of set of LaBella flats over the decades I've been a bass player (started in '76) and both the "Deep Talkin' Bass" and "Old Originals (now marketed as the Jamerson set?) have all the thump you'd want out of a bass, but after a short while they didn't have a note in the thump- sounded more like a big dog turd hitting a hot sidewalk.
The other flats I've used include:
Fender 850s (the stock string on Fender basses until 1982- they don't make anything like them now- but the Chromes might come close)- I used these for a long time until I started using modified rounds (D'Addario Half-Rounds and GHS Brite-Flats) had a note and thump, but were really stiff strings.
Dean Markley Flats- great sounding and feeling strings, not made any more, quite probably were really GHS flats but Markley now owns their own string winding machines and I used them in the '80s
Fender 950ML (I think) I had them on for three days- putrid awful strings- twangy and clashy in a bad way and very stiff. Not worth the aggravation of waiting for them to get broken in to see if they'd change.
But don't discount rounds either. I'm a big believer of letting the instrument tell me what works best for it rather than going to it with preconceived ideas of what sounds best on it. New rounds can be very useful, but I really like rounds that are aged a bit to clear some of the "scraping" kind of new string sound but still speak with clarity.
John