The road bike is 700c X 25 which is not particularly suited to gravel paths amd the mountain bike is about 195 X 29. Is has a fairly non aggressive tread suitable for most surfaces.
The mtn bike is a Reid brand which are cheap and not too nasty. Had it a few years and it has only cable disc brakes. Ok for trails but barely enough brake power on a steep descent.
Around 20 - 25 years back (in my bicycle shops days), I swapped the original 700 x 35 tyres on the hybrid for 700 x 23 HP (around 120psi) road tyres. With a few other changes, it was a very, very fast road bike, would've been even faster with a better, fitter, stronger rider. Anyway, it was good enough to take me
Around the Bay in a Day a coupla times. Mid-2020, I put on about the 4th or 5th set of the HP tyres, only done 50km on these so far.
In preparation for the Mansfield to Tallarook ride and thinking I would ride the hybrid, I've swapped back to some 700 x 38 tyres. I'm not sure if you could fit 700 x 38 tyres to your road bike, it might be worth some effort to investigate. Failing that an option may be some 700 x 28, 700 x 35 or 700 x 35 tyres, any of these would be better on the trail than the 700 x 25 tyres.
I might have a fiddle around in the garage tomorrow to see if the 700 x 38 tyres will fit on my road bike - they only need an addition 13mm clearance - it'll be interesting. If they do, you are quite welcome to try them on your bike. The logistics of this may be difficult as there is around 5km between our 5km bubbles, but when we can break-out we can have a chat.
https://www.ebay.com.au/itm/324135301574