Rust, 100 bytes, Score \$\approx 1.69863\times 10^{78}\$

The score is \$8+\underbrace{6\times(6\times(\cdots(6\times2+3)\cdots)+3)+3}_{100 \text{ levels}}=\$ 1698628421100184355851394694610950333396573647229682666011987112560692567841185.

The type is Option<((...(u8,u8,u8,u8,u8,u8),...))>, with 100 levels of nested tuples, where each tuple contains 6 identical items.

type A<T>=(T,T,T,T,T,T);type B<T>=A<A<A<A<A<T>>>>>;type C<T>=B<B<B<B<B<T>>>>>;None::<C<C<C<C<u8>>>>> 

Rust, 100 bytes, Score \$\approx 2.22128\times 10^{78}\$

The score is \$8+\underbrace{6\times(6\times(\cdots(6\times2+7)\cdots)+7)+7}_{100 \text{ levels}}=\$ 2221283319900241080728746908337396589826288615608046563246444685656290281023085.

The type is Option<((...(u8,u8,u8,u8,u8,u8),...))>, with 100 levels of nested tuples, where each tuple contains 6 identical items.

type A<T>=(T,T,T,T,T,T);type B<T>=A<A<A<A<A<T>>>>>;type C<T>=B<B<B<B<B<T>>>>>;None::<C<C<C<C<u8>>>>> 

Rust, 100 bytes, Score \$\approx 9.99073\times{10}^{45}\$

The score is \$8+\underbrace{ 2\times(2\times(\cdots(2\times4+3)\cdots)+3)+3}_{150 \text{ levels}}=\$ 9990733848941719167408001786146465954679226373.

The type is Option<((...((char,char),(char,char)),...))>, with 150 levels of nested tuples.

type A<T>=(T,T);type B<T>=A<A<A<A<A<T>>>>>;type C<T>=B<B<B<B<B<T>>>>>;None::<C<C<C<C<C<C<char>>>>>>> 

Rust, 100 bytes, Score \$\approx 1.69863\times 10^{78}\$

The score is \$8+\underbrace{6\times(6\times(\cdots(6\times2+3)\cdots)+3)+3}_{100 \text{ levels}}=\$ 1698628421100184355851394694610950333396573647229682666011987112560692567841185.

The type is Option<((...(u8,u8,u8,u8,u8,u8),...))>, with 100 levels of nested tuples, where each tuple contains 6 identical items.

type A<T>=(T,T,T,T,T,T);type B<T>=A<A<A<A<A<T>>>>>;type C<T>=B<B<B<B<B<T>>>>>;None::<C<C<C<C<u8>>>>> 

Rust, 98 bytes, Score \$\approx 7.13624\times{10}^{45}\$

The score is \$8+\underbrace{ 2\times(2\times(\cdots(2\times2+3)\cdots)+3)+3}_{150 \text{ levels}}=\$ 7136238463529799405291429847247475681913733125.

type A<T>=(T,T);type B<T>=A<A<A<A<A<T>>>>>;type C<T>=B<B<B<B<B<T>>>>>;None::<C<C<C<C<C<C<u8>>>>>>> 

Rust, 100 bytes, Score \$\approx 9.99073\times{10}^{45}\$

The score is \$8+\underbrace{ 2\times(2\times(\cdots(2\times4+3)\cdots)+3)+3}_{150 \text{ levels}}=\$ 9990733848941719167408001786146465954679226373.

The type is Option<((...((char,char),(char,char)),...))>, with 150 levels of nested tuples.

type A<T>=(T,T);type B<T>=A<A<A<A<A<T>>>>>;type C<T>=B<B<B<B<B<T>>>>>;None::<C<C<C<C<C<C<char>>>>>>>