Google Tag Manager is a tool. The odds you are using it are low. Google Search Console and Analytics both measure traffic. The reason the totals may be different can come down to many reasons including; time zones, reporting periods and more. If you want to track all your traffic as a whole, use Analytics. If you want to see Google-only traffic as a snapshot, you use Search Console. As for “Seach Console Insights’ that’s nothing more than another view of your data based on current user trends. Use it, don’t use it, it’s up to you.