Since I don't use Canon Speedlites, but use Flashpoint gear, the flash power isn't reported in exif for me to tell you the exact power I used. That would depend upon the position of the sun, brightness of the sun, and time of day, and how much diffusion I use (single, double, or triple or none). Usually I am using a large parabolic with a focusing rod that I can use to move the flash further into or out of the parabolic to focus the light on the model. I should probably start logging the flash settings for the shots when I do it and eliminate the trial and error. Usually though, it will vary from 1/4-1/2 power (usually double diffused or single diffused) and the model is always very close to the modifier (3-5 ft). Sometimes it is a single 600ws monolight in a single modifier, sometimes I'm using a 600 ws in one modifier and then dual 200ws lights in another modifier. Unfortunately, I only get to practice 3-4 times a year and this year has been terrible for doing anything at all thanks to the pandemic. I also rarely do anything in the winter. I doubt I'll be shooting anyone other than my grandson this year.
What I will do is underexpose the ambient and then light the model. I do everything in manual, no TTL because it doesn't allow me the control I want.
Yes, I could use a reflector, but I most often have nobody to hold one for me and I find they don't allow me much control of the light. Since I already own the flash and the modifiers, cost isn't an issue. My three light were under $1,500 combined.
On three photos below, no ND filter is used. I have other photos where I use either a 3-stop or 6-stop ND and the shutter speeds are considerably slower.
At any rate, it works well enough for me. I am more than happy with what I get. On the rare occasion I get a paid shoot, everyone has been thrilled. A lot of people say f/1.2 is not practical for portraits because of the shallow depth of field. I don't believe that to be true at all. Distance to subject makes all the difference.
The last photo is also f/1.2, but with a 6-stop ND @ 1/60 sec. I didn't have a 3 stop ND for that lens at the time.