IMHO, just go get some RVP50 (Velvia 50) and RDPIII (Provia 100F). Velvia has insane colours (and a very special purple for skies) that you just have to see to believe and believe me you want to see them. Provia has no reciprocity failure so you can happily shoot it at night for exposures of a few minutes whereas other slide films have reciprocity failure that varies with the channel, so the slides tend to have big colour shifts, RVP50 goes quite green in only 4s. I believe Astia is discontinued in 120 though there are still stocks to be found. It's very neutral and excellent for portraiture, whereas Velvia will give you carrot-orange skin.

Provia has high contrast, and while it's not as high as Velvia, it's very high. It doesn't have as much saturation, so that actually makes it a more difficult film to get images that really pop without blowing highlights or losing shadows. I like to use it just for twilight and night photos where the light is already very colourful.

In terms of metering, er, just don't be sloppy The easiest thing while starting out is just to shoot Sunny-16 in what you know to be Sunny-16 conditions and anything that's in direct sunlight will be properly exposed. I would suggest shooting your first roll of RVP50 at ISO50, 1/125, f/10, i.e. open up 1/3 stop from f/11 because 1/125 is not 1/100. Or combinations thereof. Whatever.

Deliberately bracket one shot from -1 to +1 stops in 0.5 stop increments (so that's five frames for one composition) on your first roll so that you have a good idea of what the slides will look like when there are exposure errors.

Once you're happy with the results at Sunny-16, I recommend using a spot meter (I use my DSLR). Anything between -2 and +2 will have decent detail, anything outside of that range you can consider to be gone or very close to it. Therefore, you want to find scenes wherein everything that matters will fit within a 4 stop range. If your tonal range is even narrower, then you can play with using half-stop under (more saturation) or half-stop over (less saturation) exposure.

6x7 chromes are a thing of beauty and I warn you that this experiment will cost you dearly!