Thanks for all of the replies! Normally I would arrive in London, or any TATL departure city the night before to make the trip as relaxing as possible. This is just a leisure trip, but my travel companions and I have a pretty full itinerary on Friday in Paris, so this time I think my travel day will have to be pushed to Saturday. It is riskier, and could be terribly expensive, but I think the risk is fairly low.

With that said, I'll play it safe and book the hour earlier than ideal Eurostar (10:30 scheduled arrival) to give myself time to transfer in St. Pancras, and allow for a buffer in case of delays. If everything goes smoothly then I'll just have extra time in the Club Lounge.

Regarding luggage, I travel semi-light, and I have taken the Elizabeth Line to Heathrow in the past with the same luggage and found it to be no issue. Nothing I can't carry up and down stairs in the stations. I'll most likely do the direct Piccadilly option. Thanks again all, and time for me to get that Electronic Transit Authorization! Cheers.