What is the typical block size in RSA? If the input text is divided into a fixed block size for encryption and decryption, what could be the typical block size for RSA algorithm for different size of input like 8 MB, 16 MB, 126 MB and 256 MB?
Well this depends on your key size.

But, in general:


A 1024-bit RSA key using OAEP padding can encrypt up to (1024/8) – 42 = 128 – 42 = 86 bytes.
A 2048-bit key can encrypt up to (2048/8) – 42 = 256 – 42 = 214 bytes.


And so on.
It is highly recommended you use at least a 2048-bit key.
If you need to encrypt more data just break it down into blocks of these sizes and send them independently (with different keys).

This however can be rather cumbersome (your server will need to have a few sets of keys) and it is best to simply send a 256-bit key (or any other size) for an authenticated encryption scheme and then use that scheme to transfer the rest of your data.