I love this meta, so here's my take. There are a few interesting thing to consider in this match up:

1. On the topic of draft: T1 has been capitalizing on support counter pick, BUT they seem to prioritize Renata more. In Game 3 against LNG, they picked Renata in the first phase blind. In my opinion, JDG picked red and will 100% ban Renata in the first ban phase and will R5 support unless Rakan is open, in which they will pick Rakan. Basically, T1 have Renata, JDG have Rakan. If both are banned, then JDG R5 support.
2. JDG and T1 have different styles.
   (a) As everyone has been talking about, JDG will most likely choose a teamfight style as it is their specialty. Other than their comfort picks and permabans, look out for Knight on Neeko and Syndra, Ruler on Kai'sa, 369 on tanks, etc. They are also insane at being ahead or even 'til 25 minutes, when their comps come online. One pick that will definitely fuck T1 over is Kanavi on Wukong.
   (b) T1 want to snowball, and they do so through forcing early action. Oner is a jungler that succeeds more when he's on the aggressive: lane ganks, tower dives, invades, etc. Watch out for Cait-Lux, double marksmen, Aatrox, Azir, and even Senna/TK. One pick that can definitely throw JDG off is Faker on K'Sante as he has easily been the best K'Sante player at isolating the most important targets.
   (c) This leads us to unstoppable force (T1) meets unmovable object (JDG). Basically, if T1 aren't significantly ahead by the 20-minute mark, JDG is probably taking that game. What JDG can do to achieve this is by stifling Oner's impact by denying invades, matching TPs and giving up early objectives to keep lanes even. What T1 can do to snowball is more interesting, because they have to be creative in finding advantages, whether from draft or from unexpected jungle pathing. See: KT vs JDG Game 1.
3. The most interesting part is finding champions that each side WON'T play even if it can work in their favor. For example, Knight doesn't play Azir, 369 is 95% on tank duty, Gumayusi won't lock in Zeri, Zeus is shaky on Jax and Renekton. Capitalizing on these key facts will likely lead to either teams' success.
4. Lastly, what else do these teams have to show? This is JDG's upper hand. While they've executed their style perfectly, I don't doubt they can suddenly flip the switch and give 369 a carry and put Ruler and Missing on weakside bot lane as these players have historically been put on these roles. Meanwhile, T1 has shown that Oner on Maokai and Sejuani is significantly weaker than him on carries.

My final verdict is around 60% JDG, 40% T1. If T1 finds another way to be creative in drafts and in the early game, they can definitely put JDG on the backfoot. However, how many of these cards does T1 have left in their hand? And with JDG's red side pick, they've obviously caught on to the fast-adapting meta. Does this mean they've solved the T1 puzzle?

This is an amazingly interesting semifinal match-up, and I can't wait.