I did 120 STR at base 99, but I wouldn't recommend it so much as I'd say it's "doable" if you plan on using spear dynamo for the extra hit. If you do go 120 at base 99 or 100, you're gonna only have enough points to get 2 other stats to about 40, which isn't going to be very easy to do if you are planning to face tank/mob.
You may want to keep STR at 100 and focus more on vit/dex for an easier time. Realistically, with level 5 IB, you'll be one-shotting most of the early monsters anyway. The real trick is getting to level 5 IB (I spammed 2nd floor eden boards while 99 and put in a few low TIs all to job xp).
If I were to remake a phys RK and level it from 100, I'd aim for stats to be something like
100 STR
50 DEX
70 VIT
30 LUCK
and the remaining 25 or so points in either INT or AGI.
From there I'd work on getting 90 VIT, and then raising STR to 120, then DEX to 90 and AGI to like 60.
I personally don't like getting INT on phys classes early on as it barely gives you any sp, and I use earth deleter + undead knight F card for sp anyway. Still, some of this is personal style stuff so see what works for you.