Why IPv4 still matters
IPv4 addresses are scarce, so they cost more than IPv6, but they reach every destination. An IPv6 proxy is cheaper per address, yet it can only talk to sites that have IPv6 enabled. If you have not checked that, start with IPv4.
All three IPv4 products here are datacenter proxies: the address belongs to a hosting network and stays the same for the rental. They are not residential, ISP or mobile IPs.
Private, shared or a mix pack
Choose private IPv4 (HQ proxy) when the address should be yours alone. Choose shared IPv4 when you want the lowest IPv4 price and can accept that up to two other customers use the same address. Choose an IPv4 mix pack when you need a list of private IPs across several countries in one order, rather than picking countries one by one.
Protocols and delivery
Private and shared IPv4 proxies accept HTTP/HTTPS and SOCKS5 on the same port. Mix-pack proxies have a separate SOCKS5 port next to the HTTP port. Credentials appear under My proxies after payment. See the SOCKS5 and HTTP setup guide.