Technical Fellow is an academic and/or research position. SMEs don't have technical fellows, although technical fellows sometimes start their own companies.
Senior/Chief Architect is an engineering/production position, with limited scope for game changing R&D. In a typical 10-20 man shop the position is usually taken by the CTO, who will be usually be in it for the long haul for both financial and technical reasons.
Very, very rarely a startup will turn into a unicorn with hundreds or thousands of employees. You can get some way up the ladder when that happens.
But the odds are against it happening in the first place. And at the higher levels you'll still be competing with talent hired from outside.
Senior/Chief Architect is an engineering/production position, with limited scope for game changing R&D. In a typical 10-20 man shop the position is usually taken by the CTO, who will be usually be in it for the long haul for both financial and technical reasons.
Very, very rarely a startup will turn into a unicorn with hundreds or thousands of employees. You can get some way up the ladder when that happens.
But the odds are against it happening in the first place. And at the higher levels you'll still be competing with talent hired from outside.