To start this, i don't know who have the AP advantage, but since High 7-A is a small tier and Tamamo don't have the "+" sign, they should be pretty comparable.
As always, Lopunny have some good Stats amps, Agility is the most notable, amping her speed making Lopunny faster than Tamamo, her Attack with Power-Up Punch and her defenses with Cosmic Power and Defense Curl. One other advantage is the fact that Lopunny can stole Tamamo's mirrors with Covet, i don't know how important that is, but i just want to point out this advantage. Alongside stats amps, Lopunny also have stats reducement, in the form of Charm and BDE to lower Tamamo's physical attack, and Fake Tears to lower her defenses. Lopunny can possibly reflect the poison with Magic Coat, and reflect most of Tamamo's attacks with Mirror Coat with double the damage. Fake Out is a guaranteed lead attack here, not to powerfull, but a neat move. The things that Lopunny here don't have, in comparition to alot of other mons, is a spammable STAB move, outside of Sky Uppercut. Loppuny seems the type of girl to use H-JK and JK more often thatn the others attacks, but if Tamamo can set up a forcefield before the hit connects with her, than Lopunny is in a pretty bad position. While Sky Uppercut is still a good move, i am pretty sure that Lopunny will crash on one of the forcefields with H-JK, and there you go most of her health. The elemental punches serve as a nice coverage moves for other moves that Tamamo can throw at Lop, Encore itself can really screw up with Tamamo, while she is not dumb, i think that adapting your plan to work with only one move is a bit hard to do. As for status, Lopunny can possibly poison Tamamo with Magic Coat, and can cause confusion, while confusion is not really that great compared to cutting in half the enemy's attack or speed, it will still help. Loppuny also have a passive speed boost with Quick Attack, though Agility should be more effective. For long range, Lopunny has Swift, Focus Blast and Hyper Beam, Swift is alright, Focus Blast will have a hard work with that accuracy, and Hyper Beam is not viable due to the need of recharge. The regen is nothing to high, and it can be bypassed, at most, it will be annoying.
Overall, while Lopunny have some good stat boost and reducement, and some powrfull moves, i still think that the fact of Lopunny crashing in a shield with H-JK is too high, and the HP lost is also to significant here to be overlooked, though Lopunny can discover the shields with other attack.
For me, i would go with Tamamo if Lopunny only spammed H-JK, but the fact that Lopunny has P-UP, Fake Out and Stats reducements, i think that Lopunny would discover about the forcefield and be cautious about them.
Voting for Lopunny Mid-diff
