Hi Keea -
Yes, nowadays with 24-bit recording [enabled in GB's Preferences], there's really no need to have maximum recorded levels above around -6 on the input meter[s]. Drums have stronger transients [impacts] which can overload [go into the red], so those tracks will likely sound lower in level, because of the required extra headroom [safety margin]. If other tracks are recorded hotter, turn them down more after recording -- if the overall playback level is softer, just turn up the listening level on the amp/speakers as desired.
In mixing, "Level Creep" is a common thing -- people keep turning tracks up one by one as they balance levels and eventually everything is too loud. A good strategy is to turn all tracks down at first so the combined level [in the meter for the Master Track] tops out at around -12 to -6. Then if levels creep up you have a little headroom. Also, it's always a good idea to get in the habit of turning levels down on other tracks rather than turning the level up on a track that's too low in the mix, still always keeping an eye on the overall Master Track level. This is easier to do in Logic than in GB -- there you can select a bunch of tracks and lower their levels proportionally all at once. [Btw, it's good practice to leave the Master Track slider at Unity Gain ±0.0, and make overall level adjustments with the track sliders, as above]
When the mix is done, you can always turn the overall level up by using mastering plug-ins [like the Limiter] on the Master Track, although that's a big topic, as standard levels in mastering are changing from "as loud as possible" to specific lower average levels required by streaming services. GB doesn't really offer those tools, only a "Normalize" option in the Preferences -- that would be fine for non-critical applications, but if you intend to submit your mixes/masters to a streaming site you'd want to read up on the subject as you get more acclimated to the technical aspects of recording/mixing/mastering..
I attached a basic GB course above, though you may be a bit past that already -- in video 16 he talks a little bit about setting levels. A more advanced course on recording drums is linked below -- it's not GB-specific but you might find it useful..