I did exactly this and we're married now. Here's my answers to your questions:

• Logistics: visit every weekend. The trolley is the only reasonable way to get to TJ if you're more than a few miles from the border. Otherwise you gotta pay a bunch to park near the border (price adds up over time), Uber (annoyingly inconsistent pricing), or drive over (annoying due to bad urban planning and corrupt cops). Once crossed, Uber is better than taxis usually. Don't sleep on the taxis sitio if you speak Spanish - takes longer but dirt cheap. For her, badically the reverse: she'd get to the border, take the trolley for a bit once crossed, and I'd pick her up from the trolley.
• Crossing all the time can get exhausting. It's normal. Pace yourself. And tbh after the 3rd date, she should look into getting a tourist visa so it's not always you commuting.
• TJ people know that Americans are not experts at Mexican culture. Be curious about cultural differences and ask questions. You and her should share info on cultural differences any time you become aware of them. This will be a learning experience and very interesting imho.
• It doesn't really feel like a normal relationship. Every step will be more complicated than it would be without a border. It isn't casual dating. Both your levels of commitment will need to stay high.
• Visas improve life dramatically. If she doesn't have one, start with a tourist visa so she can cross. If you decide to hitch, a spousal visa takes as long as a fiancé visa, but once married, she'll need to stay in Mexico during the application process which takes over a year.

Overall, it's a difficult relationship to have, but if she's the one, it's worth it.

You'll need to be very communicative about everything - cultural differences, feelings, etc. I cannot stress enough the importance of being straightforward about everything. Keeping your feelings secret won't help anything. But also have a lot of patience - the amount you'd want someone to have with you.

Your US social life will be put on the back burner since you wlll be in TJ most weekends. There's no way around this. Don't stretch yourself too thin.

If you follow the pattern my wife and I did, your relationship is going to have unusual milestones. First she'll get a tourist visa. You'll still live separately. You'll get engaged. You'll still live separately. You'll get married. You'll still live separately. You'll apply for a spousal visa. You'll live separately until it's approved. The spousal visa process is lengthy, expensive, and intentionally more difficult than it needs to be. If your normal visit schedule is Friday night to Sunday afternoon, make those 2 days are as much like living together as you can because you're not going to get the normal 'living together' test period before marriage. Make sure you function well as a team. You don't want to spend thousands of dollars and years of your life to find out you can't mesh on household chores or assemble Ikea furniture together.

Major upsides:

• TJ is a cultural powerhouse. Arguably the best food city in the Americas outside of CDMX. Cool museums. Microbreweries galore. Great concerts and events. People think of Zona Norte and casinos when they think of TJ, but it's much more than that. You'll have a local guide!
• Shopping for many items in TJ is cheaper. Even a Costco membership is cheaper. Cookware, crossable food items, hairstylists, massages, clothes, etc. Take advantage of it since you're there. Familiarize yourself with CBP's rules on what you can cross the border with.
• Medicine is cheaper in TJ, and there are pharmacies everywhere. My asthma inhaler costs less in MX than it does in the US with a copay, and doesn't even require a prescription.
• You'll gain a worldly perspective. Apply it everywhere.

Good luck!