Honestly, depends on the company and the state you're working in. It's all anecdotal, so take the following with a grain of salt.
I've worked for startups in Washington and California. In Washington, there was an invention clause in my contracts, but in practice it was a) practically unenforceable and b) as long as you divorced your work identity from your personal identity, nobody cared. This meant not having a way of tracing an anonymous handle or email to you working for the company. In California, I've never seen an invention clause in my contracts, but they were also much better at divorcing your work and personal identity systematically (forcing you to use a github account specific to the company, not mentioning this handle on your personal account, etc.).
In any case, keeping your work and personal work completely separate (no competition between work and individual ideas, no shared hardware) is a good idea and won't raise as many eyebrows. Some companies will be more aggressive about owning what you do, so if it matters to you then ask about the clause before signing the contract.