I personally hate panniers on my bike, especially the front, so I would certainly go the trailer route and make the bike one I could race with. Racing bikes are generally divided into two or three types. Criterium bikes are the most twitchy and stiffest, often with very low handlebars. Road racing bikes are a bit mellower, like what riders use on the Tour de France. Some manufacturers sell Paris-Roubaix bikes built a bit tougher and often with some sort of shock-absorbing construction to make the ride more comfortable but with the same geometry as the road racing bikes. Any of these bikes would be capable of the 1850 mile ride you're going to do.
It might be nice to get a reversible stem so that it's easy to have the handlebars higher for the long rides and lower for racing. For longer distances I like the bars approximately level with the saddle or an inch lower than the saddle. For racing I like them about 4 inches below the saddle height.
For frame materials, carbon fiber is king. I've ridden steel, aluminum, titanium, and carbon and there's something about carbon that allows it to be stiff and compliant at the same time. Of course it's expensive; you can't have everything. Steel and titanium are close seconds, so if you're on a budget, go for steel. Aluminum can be okay, but it's a harsh ride compared to the others so the long rides will be more fatiguing.
More important than frame materials are the brakes and shifters. Ultegra is my minimum and if I can't get a new bike with Ultegra at the price I need, then I would buy used. 105 is functional too (I haven't tried the 11sp 105 so I can't pass judgement on that), but I would rather ride a harsh aluminum frame with Ultegra than a nice carbon frame with anything less than 105. To be clear - Ultegra = great, 105 = good, Tiagra and under = unacceptable. Maybe I'm elitist, whatever.
I got my wife a new (previous year) carbon BMC with Ultegra for $1800, just as a point of reference for pricing.
Hope this helps and I hope you have a good trip on your new bike!