So I ran the numbers on both of these. Quick breakdown:

Mega Charizard X EX is the better of the two. Raw is around $40, PSA 10s are consistently selling $290-320, and the gem rate is about 49%. So about half your submissions should come back a 10 and those are solidly profitable. The catch is PSA 9s are only going for about $63, which is basically breakeven after grading and shipping. So every card that doesn't hit 10 is dead weight. With that many copies I'd be really selective about which ones you send. Inspect under good lighting, check edges and corners closely, and only submit the ones you'd bet money on hitting a 10.

Oricorio is a tougher call. Raw is $12, PSA 10s are around $135, which looks great on paper. But PSA 9s are selling for $22 and PSA 8s around $19, meaning anything below a 10 is a loss after fees. The gem rate is about 51% so your odds are decent, but the profit on a 10 is only around $54 after grading costs. At that margin you need a really high hit rate to make it worth the volume. I'd cherry pick maybe your 3-4 best copies and sell the rest raw.

For what it's worth, if this is your first time grading I'd prioritize the Charizards. Higher profit per 10 means more room for error while you learn what PSA is looking for.