I've been collecting continental coins for a while, and now it's time to spend them. I know the majority of the upgrades are just aesthetic, but do any of them affect the gameplay in some way?
There are some additional benefits that are not noted here. For one, you can gamble your on-hand cash in the "casino" area after upgrading it a few times -- at max upgrades it should have a few machines.
Additionally, when it comes to safe house invasions, it may be more beneficial to you have more furniture lying around as a result from upgrading specific parts of your safe house because remember, the more furniture, the more cover you have when dealing with these kinds of missions.
From what I've found, all safehouse upgrades do not impact gameplay in any way. They are cosmetic only.
One Reddit stated:
Safehouse is only aesthetic, I believe if you upgrade the garage you get new van colour options but other than that there's no real benefit.
Multiple pages stated that the garage gives you a new van color, but again, this is cosmetic only.
A Steam Post also seems to agree with Reddit.