for just browsing and occasional dms you don't need mobile proxies at all. static residential or ISP proxies will work fine for all four platforms if the ips are clean and you're not doing mass automation. the key is keeping one ip per account and not switching between accounts on the same proxy.
for TikTok desktop specifically, ISP proxies tend to work well because tiktok's desktop detection is less aggressive than their mobile app. for ig and fb, residential works as long as the ip hasn't been abused before - check the fraud score before buying.
X (twitter) is actually the easiest of the four and even some clean datacenter ips can work if you're just browsing. the "mobile proxy is required" advice mostly applies to people running farms with dozens of accounts and aggressive automation, not casual multi-account use.