You mean a Walther PPQ Q5, right? The most important questions regarding a defensive handgun for carry are: (1) is it reliable?, (2) can you shoot it?, and (3) can you carry it?
As for the first question, search the Internet. The Walther PPQ Q5 is not a handgun that people typically carry and it is certainly not a handgun that people typically trained with in the professional firearms training classes I went to. Most people decide reliability by going to a square rage, shoot 100 rounds of training ammo through it and then shoot maybe 20 rounds of carry ammo thought it. If the gun performs with minimal issues, they decide that it is reliable. I usually shoot 1,000-1,500 consecutive rounds of training ammo on different days through it without cleaning it. Then I shoot 100 rounds of carry ammo thought it. There should not be a single malfunction. Then I take the handgun to an advanced pistol training class, where the gun is fired in different positions, often in inclement weather, dropped, and exposed to dirt and other material. There should not be a single
serious malfunction that disables the handgun.
I can tell you already now that the red dot option will be less reliable than standard steel sights. I have seen a Trijicon RMR fall off in a recent training class. I have seen a Trijicon RMR lose zero too. Both are related to the fact that the screws come loose, even with Loctite. Since any backup sights are on the mounting plate, they shift or fall off too. Now, the biggest reason for that is the stress created by one-handed gun manipulation is too hard on the screws. If you don't plan to do that, you can certainly use a red dot. However, you are also certainly deficient in the gun handling department.
Speaking of one-handed gun manipulation, the slanted adjustable rear sights are a no-go as well. There is no way you can hook up that sight on a belt or any straight edge to rack the slide. You would need different aftermarket sights.
The main market for this gun is competition shooting. The ported slide just means more dirt can enter your gun easily. That's a feature you don't want to have in a defensive handgun.
The other two questions about shooting it and carrying it, only you can answer. Quite a few people carry full size handguns. I carry a Glock 20 sometimes, but a Glock 19 most of the time. The biggest factor is a proper holster and belt.