Heads up, an easy way to fairly-accurately guess what a pickup will sound like without the tone cap in play (or with a tone control, if it doesn't have one yet) is to simply imagine how it would sound if you changed pot values. Two 500k pots at '10' dulls the tone the same way one 250k pot will. Two 1 meg pots will have the same effect as one 500k pot.
Another way to think of it is that if you use linear pots (not logarithmic) and turn them to 50%, you're getting the same effect as a lower-resistance pot at 100%. So a 1meg pot at 50% is the same as a 500k pot at 10, etc. This is a bit more haphazard as even so-called linear tapers vary slightly and as pots are usually made to within +/- 10% of their stated resistance value, the 50% mark may not be quite so accurate. But again, it can get you close enough to have a fair idea of what's going on if you change the number of pots or pot values.
It's worth trying, at least once, wiring a guitar up with just a 250k pot on the pickup, and then change it to a 500k pot, and then a 1meg pot, just so you can hear the difference that change makes. Once you've done that once you should then have a good idea of what adding (or removing, as the case may be) a second pot would sound like so you can confidently estimate what is best in future.
A tone control at 10 does bleed off a fraction more treble than a volume control at 10, but it's such a small difference that I wouldn't worry about it; when the control is at maximum like that, the resistance value of the pot is what matters most.
