Sprite sheets performance

I am new to GUI and sprite sheets and I could not find here on forum some performance comparison of using sprite sheets (transparent texture containing 10x10 pictures of cycling animation for example) I plan to use sprite sheets animation in mobile android game. How should I start if I want animated GUI elements (eg player healt, status, information, interaction buttons...) all made by sprite sheets animation.

Small questions:

1. How much it depends on count of sprites in animation?

2. How much it depends on resolution?

3. Is this approach fastest? (or are other ways to achieve good animated visual)

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I also considered other possible creative solutions that can be used for a GUI MENU and in game effects:

GUI text - text drawn in space GUI texture - mostly used texture drawn in space 3D text - for some menu possibly Particle emmitor - containing one sheet of for example explosion that I put in scene

Big questions:

1. May I ask about their performance affect on the game and how I should use them in code?

2. What is the reason to use whole unity GUI for everything comparing to just draw textures and animated sheets on GUI and effects made by Particle Emmitors in scene containing animation (played just 1 time for that reason for example.

Thanks in advance help.