If using the UD interface, just set your device profile(s) to 10Gb if you have that much hard drive space and walk away. The current projects don't use nearly that much, but you will get a few more points that way. If you don't have 10Gb free, the profile should be cut back automatically.

The speed of the project is not any faster but it could be impacted by not using enough storage. The best way to increase speed is to turn off any screen savers and use (none). The energy saving features of the monitor will turn off the screen and standby after a preset amount of time.

For BOINC, the storage will be closer to what is actually used. You need enough to hold programs and workfiles, but the space used can be checked in the disk button on BOINC. Mine is set to 5GB because I am running multiple projects now and then, each of which requires some storage.

If your BOINC queue is set to a higher number of network days, you will need a higher amount of storage, and wait longer for each validation.