You can ride them. the gather rating here on thatch is underrated, I had a 150 and gathered so much thatch with it over encumbered me in less than 10 minutes may have been over 50k thatch in 10 minutes.
Feeding it what you want it to gather has NO EFFECT on its father rates. These are determined by the additional level granted every level to increase your moschops' gathering efficiency of your chosen resource.
Best for if you need fast polymer for crafting. I have used this countless times to make all the industrial equipment. But only level up health and weight and put the gathering levels into polymer. Mines at 530% and I get 50 polymer per penguin. ðŸ‘