Suppose I have lot of bitcoins on offline generated address and private key stored on paper wallet.

Now I want to spend/sell these bitcoins. What are secure and effective ways to do this?

I will need to load the bitcoins at this offline address into some wallet (say Electrum). So do I need to load all the bitcoins, or only some? How do I do it?

So I have to EITHER sign an offline transaction made by Electrum (for sending some btc to an exchange) http://docs.electrum.org/en/latest/coldstorage.html or SWEEP them to Electrum on online computer (send all btc to electrum wallet) http://docs.electrum.org/en/latest/faq.html#can-i-sweep-private-keys-from-other-bitcoin-clients

Am I right?

What the ways to spend such large number of bitcoins on offline address and private key?