Keep in mind that every level up after mastery level 5 is based on performance not on experience. You will gain infintely more experience if you continue to play after level 5 and the only upgrades will come by forging mastery 6 or 7 tokens. Those are gained by getting a rating of S- or higher for 6 and a rating of S or higher for 7. So if someone never manages to get a S- or higher with a champion but has 200k experience, lvl 5 is still his real level.
There is no way of seeing the amount of mastery tokens gained for a specific champion in the client itself if the account isn't your own. If you're looking for a method to find your own shards, you'll find them in the Loot tab. Your experience will be on the Collections tab. You'll see champion experience by hovering over the champion.
Please note that you will only see the experience of the top 3 champions of summoners you search via the chlient. The only way to find out how many champion points or "actual level" a summoner has is through 3rd party websites.
Personally I use masterypoints.com. You can search for summoners and you'll see their mastery experience and tokens.