There's a ton of ways to buy Bitcoin - exchanges, p2p trading, Bitcoin ATM, personal meeting, DEX, automated exchange services, chat bots. They all have different fees, ranging from zero to single-digit percentages. Also keep in mind the risks of scams - they are low with more reputable exchanges and high with less obscure ones or some forms of p2p trading.
The goal is to find a platform which has a less fess but some on your list has known to have a high fees like bitcoin atm and exchanges. When you say exchanges I believe it means centralized exchanges because you also have dex or decentralized exchange in your list and we all know that most centralized exchange charge a high fee.
Some in your list are also risky like chat bots, I supposed this can be found on telegram? Since, telegram is more crypto oriented right now but this platform is becoming a den of scammers lately. P2p is also risky but we are more sure in personal meeting because that is face to face. The low the fee the riskier it was. Are we really sure that we can sacrifice our security only to save fees?