The aim of a full node is to unilaterally confirm that each one guidelines of the Bitcoin protocol have been adopted, and to synchronize a node’s state with the worldwide community’s state. Protecting obtainable your complete Unspent Transaction Output set (UTXO set) is each a necessity to that finish in addition to the top itself: greater than the rest, the UTXO set represents the present state of the community.
Whereas pruned nodes can discard blockchain knowledge after processing it, as established in Why is a bitcoin node pruned to 550MB taking over 10GB+?, the chainstate database shops the UTXO set which can’t be pruned for a full node to satisfy its function. Provided that your Bitcoin listing seems to be roughly the anticipated measurement for a pruned node, and also you state that the entire talked about nodes are pruned, I believe that the reply is: you can not additional scale back the storage footprint of your pruned nodes with out impeding their perform. As to why they’ve totally different sizes, I believe that the various block intervals translate to totally different minima on what number of blocks are retained, and the networks clearly differ within the measurement of their UTXO units.
If you don’t really want a fullnode you could possibly exchange your fullnodes with third-party knowledge sources or SPV purchasers, however when you do want the performance of a fullnode, the reported numbers look like the anticipated minima.
