Obviously, there is no right or wrong answer to your first question. When you say "what your brand is worth" do you mean strictly in a revenue generated from advertising perspective?
If so, as a publisher, I would say you have some control over what your brand's inventory is worth. Having responsive web pages and choosing the right type of advertising are definitely major factors. Your site aesthetic, # of ad zones/page and the category that your content competes in are all things you can control that contribute to your brands "worth".
Wouldn't you say the end goal is to have all of your inventory directly sold? I know it's easier said than done but that would be the ultimate testament to your brand's value. If you can dictate the price of your inventory to brands/advertisers, you would be determining your brand's worth.
Check out pcper.com, they directly sell almost all of their inventory and are a good example as they can choose who they work with and what is displayed on their site.
The type of advertising is important. Teslarati.com has a ton of native inventory as native has become increasingly popular and profitable!
To address your second question:
I think being responsive to the industries trends and direction are key to controlling the value of your brand long-term. Always be willing to adopt new product/tech. I think some publishers get hesitant to implement new tech on their pages, however, adtech will only continue to innovate! Anything that provides value to your users should be utilized (ex. tech that creates a better user experience). Access to your users are what the companies are paying for after all! Staying true to your users first is what I believe gives you ultimate brand safety in the long run.