I have an H patter shifter for my Logi set (Pro wheel but still use the OE G29 pedals). I really like the extra engagement using the shifter, especially on cars in the game that are indeed a true manual. Also, some of the older cars it's much more picky on getting the shifts done correctly and slowly enough (787B for example), which makes sense as the technology in the transmission of cars back then pales in comparison to today.
GT7 does a really good job of incorporating this, IMO. Every time you put in the clutch, the HUD will show an N rather than the gear. And it's legit, as in you can be cruising at 100mph, put in the clutch while still having the shifter in 4th gear, pin the throttle and the revs will bounce off the limiter while you continue to coast; obviously this mimics real life. No one would ever really do that but what this mechanic allows is for more realistic heel-toe downshifts. You can also skip gears as well (5th to 3rd, for example).
And, it's hella fun. Especially when you take a cammed ZR1 to the ring! You can see the N pop up in the HUD in between every shift, both up and down.
I can't speak for all of the cars in the game, but I'd venture to guess if you have a clutch pedal (which G29 pedals do) then just pushing it in will yield a N within the HUD. Admittedly, I don't use it often as you can only use it in 1P mode as they've been programed out of Sport Mode, which is a bummer.
For a skill in driving which is getting more and more lost in each generation, it's cool to see it's able to be used in GT7. Personally, I love stick shift; every car I've ever owned has had three pedals to this day. But, likely the next won't as they're just being phased out of existence (at least here in the states).