Your most obvious limiting factor here will become energy since pretty much all of your farming needs to be brought inside once you get to such a scale.
Using indoor farming you need at least 110 watts/m^2 and the average person consumes about 270m^2 (when using areoponics). This means that you each person needs 29,700 watts to have enough to eat, and if we use the USA as a standard for "comfortable living" we also need to add ~1400 watts per person to power things like lights, microwaves, transportation, computers, etc. This puts the total power consumption per capita at 31,100 watts.
Since a Type I civilization can harness 1.74×10^17 watts of power, that means you cap out at about 5.6 trillion people, but future tech lighting and GMOs might be able to push this number even higher without having to sacrifice modern food diversity.
This introduces two other limiting factors which are building materials and global warming.
Since Earth has a total land mass of 510.1 trillion m^2, this means that if everyone lives on Earth, you'll have a total population density of 1 person per 91 square meters. Between recreation, industry, residential space and infrastructure, your average urban resident needs about 200m^2 worth of space in addition to the farming totaling ~470m^2. If you only build on land, this means that doing this will result in an average building height per square meter of about 17.2 stories. Since about 50% of any city is open spaces (roads, parks, etc.), this means that your average occupied square meter of the planet will have a 34 story building on it.
Making reasonably luxurious buildings that tall might be doable with some nice future tech materials, but not on that scale. The entire Earth's crust does not have enough of certain materials to sustain ideal levels of comfort; so, you can assume that you'll need to do a lot of space mining to get all the copper, lithium, etc such a civilization would need, but it may be doable if your tech allows for it.
Once you start building all these mega structures and roads and parks, there is no way to actually get 100% power efficiency from just solar. Even if future tech solar is close to 100% efficient, and you put it over every building and roadway completely blocking out the sun to all of humanity, there is still that 70% of the world that is oceans. One way or another, you'll need to use something other than sunlight for most of your power. Let's say you do 30% solar and 70% super clean fusion reactors. All those reactors are generating massive amounts of heat. As far as the people on the surface of the world are concerned, this is no different than turning up the sun by 70%. YIKES!
This means that your Type I civilization will need to be able to radiate out all of that heat. The best way to do that may be to reverse global warming and build up the world to have an opaque atmosphere that reflects more sunlight, but this reduces the effectiveness of your solar power. Any way you cut it, 1.74×10^17W is the theoretical hard cap on how much power we can make without cooking the world, and that is assuming all other environmental factors can be 100% controlled for.
In reality though, solar will never be 100% efficient and the atmosphere will never be made 100% opaque; so, it's probably best to just say your civilization maxes out on the solar power of all available land mass (5.22×10^16) at about 25% efficiency (1.305×10^16), and your population caps at about 420 Billion. A Type I civilization probably can not exist on a single planet, instead, most of your civilization's power will actually be produced/expended in space. Anything beyond that is going to be VERY hard to keep cool without some pretty hand wavy mega-structures