I am using an HTTP generator, yy025, plus a TCP client, not FF, Safari or Chrome. The HTTP generator is written by me.
The TCP client is typically Al Walker's original netcat, djb's tcpclient or haproxy's tcploop (modified). But any TCP client will work.
I generally use haproxy and tinyproxy-stunnel as TLS forward proxies. The former lets me monitor all HTTPS traffic from computers I own over the the network I own and modify headers, cookies, URLs, response bodies, prevent SNI, etc. (Most use haproxy as a reverse proxy.)
I do not make remote DNS queries immediately followed by associated HTTP requests. They are separeted in time. The DNS data is gathered in bulk from varied sources periodically. I do this with software tools I wrote myself that are designed for HTTP/1.1 pipelining. The domain-to-IP mappings are stored in the proxy's memory. There are no remote DNS requests when I make HTTP requests.
I use a modified text-only browsser as an HTML reader. It does not auto-loead resources, process CSS or run Javascript.
I do text processing on bulk HTML and DNS data, e.g., from HTTP/1.1 pipelining, with custom filters I wrote myself to produce SQL, CSV and other formats.
This is only a sample of things I do differently according own specific preferences.
The so-called modern browsers cannot do all of these things in combination, as separate programs. In some cases, e.g., HTTP/1.1 pipelining, real-time monitoring of HTTPS traffic in plaintext, even something as simple as preventing SNI from being sent, these browsers cannot do them at all, even with extensions. The so-called "modern" browsers are enormous by comparison and ridiculously complicated. They are distributed by corporations invested heavily in online ads.
Perhaps the most important difference is that I can compile each of the software tools I use in minutes, in most cases less than one minute. I can easily edit the source code in an edit-compile-test loop to address issues that arise and to suit personal preferences. This is not feasible with the so-called "modern" web browsers. Trying to compile these so-called "modern" browsers from source is excruciatingly slow. I can compile UNIX kernels with complete userlands, an entire OS, faster, easier and with only minimal resources (CPU, memory, storage).