Hello.

5 watts, and a mobile or portable antenna?
For HF "I" feel that this is not enough power.
The reason I say this is simple.
First you are already at a disadvantage, your antenna will be where you can put it, that means no real control over where you can radiate from.
A fixed user gets to pick his location to some degree.
Second is the antenna itself, clearly a limitation.
A fixed user can erect a tower in most cases, and even that disguise flagpole and dipole is going to be far better than anything you can carry in a tote bag.
Finally is the issue of background noise, more power brings you up over the hump.
QRP is fine but limiting.
With that in mind I would suggest that you explore before you buy, see if QRP is where you want to go.