It is a very high risk of getting linked, You want to make sure you have separate User accounts made on computer(s), This will make sure that the cookies are kept separate from each account.
You want to make sure you change IP's and log those IP's every time you change between accounts. VPN's aren't needed in this case, but if you can't for some reason change your IP on your modem you can do the following:
1. Use a Smartphone and Tether to your Computer(s)
OR
2. Use a Dongle which will give a wider range of IP's (I recommend this one more)
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