I have a few questions about the transaction for Bitcoin.

I have this x Hierarchical Deterministic wallet, then that x wallet, after I receive a bitcoin, I am changing/automatically changing my receiving address to another again and will use that new address to receive another bitcoin.

For example.
After those many transactions from multiple receiving addresses, I decided to send all my bitcoin from my x wallet to another wallet.
So, my total input in a transaction are all the addresses that still have unspent bitcoins.

My questions are:
1.) What are the pros/cons of changing my receiving address for every time I receive a bitcoin to my Hierarchical Deterministic wallet?

2.) I also noticed that if you have much input in one transaction, the transaction size gets bigger, then it requires some huge fee to confirm my transaction.(Let's say my example transaction above is executed).
       - How can I prevent or solve this problem (having a huge fee)?