1 - Throw the word "bottleneck" out of your vocabulary, as the word is badly misused/misinterpreted. It is impossible to lose performance when upgrading to a more powerful video card. Ignore bottleneck-calculator sites, they are worse than useless.
2 - I will say that for max details at 1080p, assuming your monitor maxes out at 60Hz (thus, can't smoothly display more than 60fps), then the rtx 2060 is overkill, and a GTX 1660Ti, or possibly even a GTX 1660, will be more than sufficient, while saving you some money. If your monitor is a higher refresh rate, and you want the higher FPS that such a refresh rate allows, then I'd have to recalculate a little.