I left legroom on mine.. and never use it ... wish I had a done something else. I just can't cut fabric sitting down... just like ironing ... I have to stand.
Regarding the height do what works for you ! I am short and mine is slightly lower than the counters in my kitchen. If you think you want them taller , try cutting a liitle on you ktichen counters and they are taller than most tables. But it is harder to cut a large piece to the very middle on really tall tables .. as you just can't get good downward pressure on the rotary cutter. See what works