The mod only changes the DIRECT effect of any room stat changed, not how that stat affects Impressiveness (which is used for most mood bonuses, so is often what you are aiming for). This is because Impressiveness uses the actual numerical values, which this mod does not change.

For example, you could have Wealth, Space, Beauty, and Cleanliness all registering as extremely amazing, yet still only have Dull Impressiveness at 22. You can test what mood bonus you get with a bedroom easily enough.

However, changing what Impressiveness itself uses for the effect WILL affect the mood bonus. So, you could have a room that is awful in Wealth, Space, Beauty, and Cleanliness, with an Impressiveness of just 10, however, if you set 10 Impressiveness to be Wondrously Impressive you'll get Wondrously Impressive mood bonuses.

The problem with this is that often the reason you want to change a room stat is because you disagree with how it affects Impressiveness. The goal, I suspect, for most people will be to change how one or more room stats affect Impressiveness, not directly choose what numerical value of Impressiveness gives what bonus.

For example, if you have an EMPTY 4x5 bedroom, which is bigger than my actual bedroom (given the relative size of the items in there, like the bed, I would estimate my bedroom to be about 3x5 in Rimworld), this is only Rather Tight in the Space stat at 28 (and it will only decrease from there as you add stuff to it). This really brings down the calculated Impressive stat.

To me, Rather Tight would be something along the lines of 3x3 with a queen-sized bed in it - leaving room for walking around it but nought much else. My actual bedroom (again, about 3x5 in Rimworld) has my desk, queensized-bed, cupboard, dresser and still ample room to move around - it is definitely not Rather Tight. Hence, I would rather such a room be classed as Average-Sized and affect the Impressiveness appropriate for that, rather than for Rather Tight. However, no matter what I do with the Space stat in this mod the Impressiveness will not change.

TL;DR: If you want to affect Impressiveness, modify Impressiveness DIRECTLY - changes the other stats will just be window-dressing.