I did not recently consider moving to the US but I can relate my story about having moved from the Netherlands to Germany last year. My wife and I made the move from Amsterdam to Berlin. Both of us are working full-time and we have a daughter in kindergarten. We were both born and raised in different parts of Bavaria with our parents still living there. Being closer to family is also a recurrent topic for the same reasons you mention. To some extent this matches one of your possible scenarios quite closely.

From my perspective I can list a few things to consider in random order:

There are are definitely good opportunities for tech jobs in some regions of Bavaria. This is especially true for the metropolitan areas in and around Munich, Nuremberg, etc. You probably know better about the market in the exact region you are considering to move to. Some of the rural areas unfortunately don't have many jobs though. The pay is also lower in rural areas — on the bright side: so are the costs of living.

Working remotely is a way to earn more and you say that you are considering remote work already. When applying to remote positions the the pay which you can expect from a German employer might not matter so much. You could potentially also apply to remote positions elsewhere, e.g. even in the US (some companies don't have strict timezone requirements). I personally stayed with my Dutch employer through a payrolling service.

In any case, when living in Germany you will need to pay income tax and social security payments in Germany. Consequently, net salary is lower in Germany compared to the Netherlands (for the exact same gross income in my case). Especially health insurance costs significantly more. In turn, you also get more government benefits.

One of these benefits is the "Elterngeld" which seems to be relevant for you and you probably know of. This parental allowance is paid for up to 14 months during parental leave for one or both parents. The amount is based on your net income during the 12 month prior to the birth of the child. Income in other EU countries also counts AFAIK. You receive about 2/3 of your previous net income. It is capped at 1800 EUR/month and you don't receive any if your net income is higher than a certain limit (which I vaguely remember to be 250k/annual net per parent).

Since you are considering moving to rural Bavaria: Mind that childcare is far less pervasive than in the Netherlands. Creches might not exist close to you and daycare usually has shorter hours than the ones in the Netherlands. Even in primary school you might need to find someone to take care of your children in the afternoon. This seems to be possible in your case with family potentially being close by.

Regarding your fear of not building enough wealth: There is definitely more state mandated welfare in Germany than in California. That includes pension. The general notion however is that it is still required to build up your own funds for retirement. Many people do so by buying a house or investing in ETFs, etc. Buying real estate for a family of four in small towns and villages should be doable on a tech salary. In cities you will likely need to make compromises.

One thing to also keep in mind: broadband internet is not pervasive in rural Bavaria. In most cases it is good enough and many communities also have proper fiber deployed but I know plenty of people who struggle to get acceptable internet access — not great when working remotely.

Germany and the Netherlands have a treaty to avoid double taxation when you move between the countries. A tax adviser is helpful in this scenario. I cannot tell you much about my experience yet because I am only in the process of filing taxes for the year of our move.

Your question about quality of life can only be answered subjectively. I personally value the safety net that is the German welfare state. For instance I never in my life worried that I would get bankrupted by a medical bill. The same is true for job safety: yes, it is possible to fire employees and temporary contracts are a thing to some extent. However, employment contracts are regulated and I feel job security is balanced more in favor of the employee than in the US. Also the parental allowance which I mentioned above is great for families.

Quality of life depends on your immediate surroundings as well. For instance, with the Covid pandemic I've found it relatively hard to meet people in Berlin. This affected quality of my life. In a small village you might struggle meeting like-minded people.