You can order your tickets s day or two before your visit. If you come to the museum at the opening hour, the crowds will be thinner.

Our most recent to Florence was last September. We had timed tickets for every museum we planned to visit as we didn't want to wait in line for an hour and waste any time that might mean missing another site. The advanced tickets certainly helped at a couple sites, when we were able to bypass the line rather than spending time in line in the rain and enter at our timeslot. We went to the Palazzo Pitti early on a Sunday morning, and I don't recall seeing a line. Certain times of year and certain days and times might require advanced tickets more than others. Good luck!

You cannot

Neither the Uffizi not the Palazzo Pitti are churches so yes, you can wear shorts though probably not at this time of the year (January) as it's really cold in Florence right now! Keep in mind that there are a lot of truly amazing churches in Florence so you might want to pop into one after visiting a gallery or museum in which case better not to wear shorts if that's a possibility. How that helps. Ciao.

Consiglio di prenotare. La prenotazione anticipata le consente di avere la precedenza all'ingresso.

I believe while the palace closes at 6:50, last entry is 6:00 - I found similar restrictions across a number of venues and attractions in Florence, where 2 times are typically quoted; a “closes at”, and a “last entry” at time.

Yo compré la Firenze-Card, que incluye este museo y jardines. Esta tarjeta cuesta bastante dinero, es recomendable si uno piensa pasar varios días en Florencia. De todos modos, la línea para ingresar era de 10 personas (julio/2019). J'ai acheté la Firenze-Card, qui comprend ce musée et ses jardins. Cette carte coûte beaucoup d'argent, c'est recommandé si vous prévoyez de passer plusieurs jours à Florence. Quoi qu'il en soit, la ligne à entrer était de 10 personnes (juillet / 2019).

It’s best to do it ahead of time and best with the guide. We were there in peak season and there was no line so either way you can do it