What is your "advertised" (what you're paying for) speed?
TP-Link stock firmware uses hardware NAT, so you would notice a difference.
Currently, only mt7621 devices support it on OpenWrt.
I use a C7 V2, which is close to your V5.
The CPU's on those devices will give you about 150 - 200 Mbps on the top end, so you're actually getting better than that.
When I move up to the next ISP speed tier, I'll be "retiring" the C7.
If you want more out of your connection, you'll need a new router.