Your observations are correct. Blockchain performance and speed can be affected in various ways, such as by network congestion, transaction numbers, and scalability solutions. As Solana claims a high speed, network congestion can hinder its performance. As for the Bitcoin network, it is limited in terms of processing speed, as it mainly focuses on security and stability. Ethereum itself is adopting various updates and scalability solutions to reduce transaction speed and fees. By testing the networks and monitoring their performance in real time, you can more Understand well which one is best according to your requirements. Primarily, it depends on the users' experience, and each blockchain has its own advantages and limitations.
As it is I only know of Bitcoin as the most fastest and cheapest blockchain in the cryptocurrency space. I made a transaction in bitcoin blockchain with 3 sat/vb and the transaction fee was (0.83). TON which was free for transaction in exchanges now charges $1 though TON network is fast but, but as Bitcoin for now. As for the Ethereum and Solana since their networks were messed up, I abandoned them so I don't know their latest transaction speed and fees.
If you remember vividly, Solana network which some people feel is the fastest network and scalability solution blockchain network has experience down time(system crash) unfortunately, many users were stranded.for hours. I think the whole issue of fastest transactions blockchain networks depends on the number of users at any point, when is influs of huge crowds of users at certain point, the system may be unable to function properly and could result in system brake down.
In my opinion, Speed, scalability, and other transactions features depends mainly on the number of users.