What type of master should I send?

Your engineer determines this. Roger is partial to a well recorded analog 1/2” 30 or 15ips master. However, it is to be utilized only by a recording engineer with experience using that format.

Is it all right to Eq and compress the overall mix?

Some experienced engineers have gear that they use to complement the mix.  We suggest not using additional processing if the engineer is somewhat new to mixing.  A common problem that occurs is over use. We suggest that engineers do not sacrifice the timbre of instruments or the dynamics of a mix for the sake of volume. Also keep in mind that it’s always easier to add or subtract the amount of processing if it is done in mastering.