Weight and balance in the G450 is pretty close to being a no brainer, so long as you don't carry any particularly heavy baggage loaded in unusual places. You need to consider weight and balance to compute takeoff trim, and of course you will need to have the numbers if you are flying under 14 CFR 135. For a primer on how to do all this, see: Weight and Balance Principles.
Everything here is from the references shown below, with a few comments in an alternate color.
[G450 AFM 1-03-70]: Zero fuel gross weight CG must be within the allowable zero fuel gross weight CG envelope. The fueled airplane CG will then be within limits for all fuel loads.
The baggage compartment is limited to 65 lbs per square foot. (If you stand with your feet together, you actually exceed that limit!) The total limit is based on the space available after outfitting and will be placarded, for example:
Gulfstream G450 Airplane Flight Manual, Revision 35, April 18, 2013
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