The mild hybrid will be much better around town or at speeds lower than about 70Km/h, tootling around a parking lot will be where you gain the biggest saving on fuel consumption. Open road, and urban arterial at 80+Km/H the hybrid won't provide enough power to drive the vehicle at those speeds and the power will come from the ICE side with the slight disadvantage of the alt system charging the hybrid battery until it's fully charged.
This is the main issue for me with hybrid and ev tech, I roll out of my house into 100 and 80Km/H zones, up hill, then a short coast down followed by 100Km/H State Highway and arterial then into where I'm parking. For something like an older Leaf with 100Km around about range between charges, the useage style is the worst option you can have as it's straight away from cold up to 100 then 80Km/H, then no regen from braking in start stop traffic and at full drive, then parked. Back home is the long slog straight up the hill to home at 80Km/H the whole way, no regen there so if the thing is claiming 100Km range around town we actually only achieve around 75-80Km before we are beating feet looking for a plug. PHEV if you can't be arsed plugging it in or HEV is similar - straight up to open road speed means not using the hybrid system only as it's not usually got enough go to solely power the thing at highway speeds, and the useage requirement for our area means the people around us who have had them have not achieved anywhere near manufacturer's claims and chewed through tyres and that side faster for their trouble.
We got a 2021 Outlander, the neighbours we had (since gone to Aussie) had a 2020 Outlander PHEV same version, just hybrid and same drive just one driveway closer to town. We were returning average fuel consumption of 6.5-7.1L/100Km, theirs was returning 5.5-6.5L/100Km. The extra sticker price for the PHEV over the ICE version buys about 3.5 years of petrol at current prices, and we save on tyres etc etc. Servicing costs are basically identical as it's the same engine effectively, and servicing intervals are on Km traveled not engine hours so no saving for the short amount of time we would be on hybrid system only...
