At those speeds, I wouldn't worry about a full-face helmet. Those are completely ordinary cycling speeds for a road cycling enthusiast. Your primary risk is probably rear and side impacts. Your body is really good at instinctively protecting the head, so you should worry more about surprise impacts, like t-bones and rear-ending.
I don't know what your helmet looks like, but modern cycling helmets have migrated toward a longer back side for better rear impact protection.
For what it's worth, one of the reasons that my motorcycle has a big top box and aluminum panniers is simply to store my gear when I get to my destination. Thieves suck and if something can be stolen, someone will steal it.
The stats for collisions from rear are surprising, rarest way to get hit on a bike (and most of those are no lights at night).
It turns out, moving closer to the center of the lane reduces the chances of the most likely directions of impact - namely turning traffic. Either turning left as an oncoming vehicle, turning out from a side road or driveway, of someone that is overtaking you and then turns right.
I've found low speed crashes really want a helmet. Things like you roll sideways off the bike. You are not moving fast but are rotating quickly. (So back hits ground followed by back of head)
FWIW, I just noticed the common irrational rational fear of being run over from behind. It is a common mistake. Riding to the extreme right can make it worse, it is an invitation to pass when instead the cyclist is just afraid. Taking a little more room on a road (situationally) can make a person a lot safer.
I may ultimately stay away from full face helmets, but surprise impacts like t-bones and rear-ends are precisely why I find full face helmets appealing. For one, I can't really control how I fall in a surprise crash. And two, I'm less worried about the initial impact, and more about being slammed into the pavement. Especially from a higher center of gravity like I have on my standing scooter. Being rear-ended and slamming my head back against the hood of a car will hurt, but my current helmet will probably suffice for that. Being slammed forward into the ground, it seems like my face will become very familiar with the pavement.
Another instance that a full face helmet seems appealing is in in getting doored. I often don't have a choice but to ride near a bunch of cars parked on the street.
Road cycling enthusiasts are a good reference point, but the differences I see are in that I am not as focused on being aerodynamic and lightweight, since I have an electric throttle doing 100% of the work for me. In the tradeoff between efficiency and safety, I have the luxury of leaning much more into safety before negatively impacting the ride itself very much. Most of the negative impacts of additional safety gear are on either end of the ride (gearing up and down)
For one, I can't really control how I fall in a surprise crash. And two, I'm less worried about the initial impact, and more about being slammed into the pavement.
Like I said, the body is really good about protecting the head. You need to focus on the initial impact. The back of your skull slamming into a windshield or truck hood is a far bigger concern than falling on your face, when you have arms and neck muscles to protect you.
At those speeds, I wouldn't worry about a full-face helmet. Those are completely ordinary cycling speeds for a road cycling enthusiast. Your primary risk is probably rear and side impacts. Your body is really good at instinctively protecting the head, so you should worry more about surprise impacts, like t-bones and rear-ending.
I don't know what your helmet looks like, but modern cycling helmets have migrated toward a longer back side for better rear impact protection.
For what it's worth, one of the reasons that my motorcycle has a big top box and aluminum panniers is simply to store my gear when I get to my destination. Thieves suck and if something can be stolen, someone will steal it.