drivetrain size
 

Hello, I'm looking to purchase 170mm crank arms, and wanted to find out what size chainring would fit these(tooth/bcd)? Also trying to find out what type bolts are used to put the two together? All suggestions welcome, Thanks.

could be any, without knowing the exact crank, could be road, mtb, compact, standard, single speed etc. all the info you have asked for should be avaliable from the crank manufactuer, when you know what you are getting.

Would look at buying a crank with rings on if possible, as this is always cheaper than buying parts

170 is just the crankarm length, bolt circle diameter is a separate dimension

Almost, if not all cranks are available in 170mm. The chainring availability is determined by the bolt circle diameter, and the number of speeds, ie 9s 10s, it's designed for.

Since 170 is so common, start with what style, road or mtb, single, double or triple, the chainring sizes wanted, and the number of speeds. That will drive you to a selection of cranks and you can make the selection.