Hey @arjunkhankriyal,
my personal approach is creating/using only custom modules and custom themes (I’ve created my own boilerplate for this).
Depending on the clients requirements this can be quite a task, but this allows you to fully dig into every little bit of code and work on a whole different level of granularity.
My best friends for such are if-statements/booleans, choice-fields, variables and often export_to_template_context as well as
A practical example:
If I’m building something simple like an accordion, I’m putting the static JS part into something like an accordion.js file in my theme and referencing it with the require_js function (I like to keep all JS/CSS in one place rather than using module.js/module.css).
Then is the CSS - not as a high impact on performance - but this still can sum up.
If the module got tons of styling options, I don’t need everything to load every time - therefore I’m wrapping corresponding parts in if-statements and choice-fields like
{% require_css %}
<style>
{% scope_css %}
.module{
border: 5px solid red
{{module.styles.padding.css}}
}
{% if module.some_choice == "option_a"%}
.module.option_a{
background-color: {{module.styles.background-color.css}};
}
{% elif module.some_choice == "option_b" %}
.module.option_b{
border-color: {{module.styles.background-color.css}};
}
{% end_scope_css %}
</style>
{% end_require_css %}
...
<div class="module {{module.some_choice}}">
your content
</div>
You can do something similar to JS (only in module.html or templates)
{% require_js %}
<script>
{% if module.some_choice == "option_a"%}
//some script which should be applied when option A is selected
{% elif module.some_choice == "option_b" %}
//some script which should be applied when option B is selected
</script>
{% end_require_js %}
There are countless options here - just be a bit creative and think this way:
Anything that is an “if question” can be put into an if- or unless-statement. Different options are choice-fields.
Build the whole structure with it (don’t forget to use comments in the code)
Reusable blocks accross modules can be put into macros
If you want to learn more about such approaches, we/the Developer HUG had a great event about Mastering HubL (YouTube recording) a while ago.
As for the realistic maximum achievable mobile score: Yes, 100% 
It’s a ton of work, but possible. Two years ago, when I launched my website (graphispot.com) I’ve set my own goal to optimize it to 100% on mobile and desktop. Honestly - it was quite a lot of work.
Since then, Google has changed their Lighthouse algoritm and because of this, my performance dropped from 100 to around 65/70. For now, I’m fine with it as I’m already working on a new website/theme.
Reducing the content on mobile is an option to optimize for performance, but not the best UX. Neither for the business, nor for the visitor.
My recommendation is to replace videos with linked images which trigger the video (or lead to the externally hosted video), forms is something we’ve discussed in the other topic.
But honestly - don’t rely on the numbers. A blazing fast website, can be so fast that the performance will show you some bad scores.
Just do some real-life tests. Grab a mobile device, open the URL and see if there are some layout-shifts or something you can actually optimize.
Hope this helps
best,
Anton
