i'm tired of repeating my answer to this question over and over. let me try quick summary this time: 21s are 100-400% faster wear rate than 19s (expect replace every 5-20k vs 40-50k for 19s), much more expensive, noisier, rougher ride, prone to [tiire] damage, prone to [wheel] damage from potholes, prone to curb rash [wheels], they reduce range, SUMMER TIRE ONLY (not to be worn during cold winter...VERY DANGEROUS), so expect flats, tow trucks, many inconveniences, and a very high cost of maintenance [tires+wheels]. but hey, they look cool.
if you want the cool look of the 21s but in 19s instead (so without any of those issues described above), you could get these instead
Tesla Wheels For Sale | T Sportline Model TST Wheel 19x85 (I have these in grey mounted on my P85 w\ Michelin Pilot Sport A/S 3 255/45ZR19s). these wheels closely match OEM specs and passed extensive testing (results posted in other threads). my 2c. honestly, i love the looks of the 21s, but I'm just not willing to deal with any of the above issues or fork out a ridiculous amount of money for upkeep.