Slow display, slow serial, or slow library?

Hi all,
I recently started to work with a 3.5" enhanced display, connected to a Teensy 3.5, in the context of a development of a small music sequencer.
No problem whatsoever regarding the editor, and the interconnection with the Teensy. I use the Easynextion library, which makes things rather straightforward (
However, I wonder what sort of performance I can realistically expect from this display. I update regularly some text boxes, depending on the musical events happening along the timeline (see picture)
I have tried to update around 200 of these text boxes , each of them with 2 characters, sent from the Teensy as strings, and it’s lagging. Baud rate on Teensy and Nextion is 921600 (works fine btw). Tried as well with a rate of 250000, and it’s as expected a bit slower.
I have no experience with those, so are my expectations simply unrealistic, or did I overlook something?
Thank you for any ideas or advices.

Using 200+ text boxes and addressing these one by one creates a horrible overhead. Take for example “t125.txt=7Fÿÿÿ” which makes you sending 14 bytes for an effective payload of only 2 bytes information.
What about packing your data into 32bit integers which corresponds to 8 characters, updating a pre-declared global variable with this over serial and let the Nextion code parse and display it?

Hi Fjodor,
Thank you very much, that makes totally sense. I basically need to send the current state of the sequencer every 16th note (that is 8 times / second, if the tempo is 120 bpm). Will see how that works.
Thanks again.